diff --git a/coretk/coretk/app.py b/coretk/coretk/app.py
index bc3ac9dd..185e5968 100644
--- a/coretk/coretk/app.py
+++ b/coretk/coretk/app.py
@@ -15,21 +15,16 @@ from coretk.toolbar import Toolbar
 class Application(tk.Frame):
     def __init__(self, master=None):
         super().__init__(master)
-        self.style = ttk.Style()
-        self.setup_theme()
+        # widgets
         self.menubar = None
         self.toolbar = None
         self.canvas = None
         self.statusbar = None
-        self.is_open_xml = False
-        self.size_and_scale = None
-        self.set_wallpaper = None
-        self.wallpaper_id = None
-        self.current_wallpaper = None
-        self.radiovar = tk.IntVar(value=1)
-        self.show_grid_var = tk.IntVar(value=1)
-        self.adjust_to_dim_var = tk.IntVar(value=0)
+
+        # setup
         self.config = appconfig.read()
+        self.style = ttk.Style()
+        self.setup_theme()
         self.core = CoreClient(self)
         self.setup_app()
         self.draw()
@@ -37,20 +32,27 @@ class Application(tk.Frame):
 
     def setup_theme(self):
         themes.load(self.style)
-        self.style.theme_use(themes.DARK)
+        self.style.theme_use(self.config["preferences"]["theme"])
         func = partial(themes.update_menu, self.style)
         self.master.bind_class("Menu", "<<ThemeChanged>>", func)
-        func = partial(themes.update_toplevel, self.style)
-        self.master.bind_class("Toplevel", "<<ThemeChanged>>", func)
 
     def setup_app(self):
         self.master.title("CORE")
-        self.master.geometry("1000x800")
+        self.center()
         self.master.protocol("WM_DELETE_WINDOW", self.on_closing)
         image = Images.get(ImageEnum.CORE, 16)
         self.master.tk.call("wm", "iconphoto", self.master._w, image)
         self.pack(fill=tk.BOTH, expand=True)
 
+    def center(self):
+        width = 1000
+        height = 800
+        screen_width = self.master.winfo_screenwidth()
+        screen_height = self.master.winfo_screenheight()
+        x = int((screen_width / 2) - (width / 2))
+        y = int((screen_height / 2) - (height / 2))
+        self.master.geometry(f"{width}x{height}+{x}+{y}")
+
     def draw(self):
         self.master.option_add("*tearOff", tk.FALSE)
         self.menubar = Menubar(self.master, self)
diff --git a/coretk/coretk/appconfig.py b/coretk/coretk/appconfig.py
index 67f97181..e8f5db6e 100644
--- a/coretk/coretk/appconfig.py
+++ b/coretk/coretk/appconfig.py
@@ -6,6 +6,8 @@ from pathlib import Path
 import yaml
 
 # gui home paths
+from coretk import themes
+
 HOME_PATH = Path.home().joinpath(".coretk")
 BACKGROUNDS_PATH = HOME_PATH.joinpath("backgrounds")
 CUSTOM_EMANE_PATH = HOME_PATH.joinpath("custom_emane")
@@ -68,6 +70,7 @@ def check_directory():
         editor = EDITORS[1]
     config = {
         "preferences": {
+            "theme": themes.DARK,
             "editor": editor,
             "terminal": terminal,
             "gui3d": "/usr/local/bin/std3d.sh",
diff --git a/coretk/coretk/dialogs/canvasbackground.py b/coretk/coretk/dialogs/canvasbackground.py
index 7b1dd186..8fb92c8b 100644
--- a/coretk/coretk/dialogs/canvasbackground.py
+++ b/coretk/coretk/dialogs/canvasbackground.py
@@ -1,27 +1,19 @@
 """
 set wallpaper
 """
-import enum
 import logging
 import tkinter as tk
 from tkinter import filedialog, ttk
 
-from PIL import Image, ImageTk
+from PIL import Image
 
 from coretk.appconfig import BACKGROUNDS_PATH
 from coretk.dialogs.dialog import Dialog
+from coretk.images import Images
 
 PADX = 5
 
 
-class ScaleOption(enum.Enum):
-    NONE = 0
-    UPPER_LEFT = 1
-    CENTERED = 2
-    SCALED = 3
-    TILED = 4
-
-
 class CanvasBackgroundDialog(Dialog):
     def __init__(self, master, app):
         """
@@ -31,11 +23,11 @@ class CanvasBackgroundDialog(Dialog):
         """
         super().__init__(master, app, "Canvas Background", modal=True)
         self.canvas = self.app.canvas
-        self.radiovar = tk.IntVar(value=self.app.radiovar.get())
-        self.show_grid_var = tk.IntVar(value=self.app.show_grid_var.get())
-        self.adjust_to_dim_var = tk.IntVar(value=self.app.adjust_to_dim_var.get())
+        self.scale_option = tk.IntVar(value=self.canvas.scale_option.get())
+        self.show_grid = tk.BooleanVar(value=self.canvas.show_grid.get())
+        self.adjust_to_dim = tk.BooleanVar(value=self.canvas.adjust_to_dim.get())
+        self.filename = tk.StringVar(value=self.canvas.wallpaper_file)
         self.image_label = None
-        self.file_name = tk.StringVar()
         self.options = []
         self.draw()
 
@@ -57,6 +49,8 @@ class CanvasBackgroundDialog(Dialog):
     def draw_image_label(self):
         label = ttk.Label(self.top, text="Image filename: ")
         label.grid(row=1, column=0, sticky="ew")
+        if self.filename.get():
+            self.draw_preview()
 
     def draw_image_selection(self):
         frame = ttk.Frame(self.top)
@@ -65,7 +59,7 @@ class CanvasBackgroundDialog(Dialog):
         frame.columnconfigure(2, weight=1)
         frame.grid(row=2, column=0, sticky="ew")
 
-        entry = ttk.Entry(frame, textvariable=self.file_name)
+        entry = ttk.Entry(frame, textvariable=self.filename)
         entry.focus()
         entry.grid(row=0, column=0, sticky="ew", padx=PADX)
 
@@ -84,42 +78,43 @@ class CanvasBackgroundDialog(Dialog):
         frame.grid(row=3, column=0, sticky="ew")
 
         button = ttk.Radiobutton(
-            frame, text="upper-left", value=1, variable=self.radiovar
+            frame, text="upper-left", value=1, variable=self.scale_option
         )
         button.grid(row=0, column=0, sticky="ew")
         self.options.append(button)
 
         button = ttk.Radiobutton(
-            frame, text="centered", value=2, variable=self.radiovar
+            frame, text="centered", value=2, variable=self.scale_option
         )
         button.grid(row=0, column=1, sticky="ew")
         self.options.append(button)
 
-        button = ttk.Radiobutton(frame, text="scaled", value=3, variable=self.radiovar)
+        button = ttk.Radiobutton(
+            frame, text="scaled", value=3, variable=self.scale_option
+        )
         button.grid(row=0, column=2, sticky="ew")
         self.options.append(button)
 
-        button = ttk.Radiobutton(frame, text="titled", value=4, variable=self.radiovar)
+        button = ttk.Radiobutton(
+            frame, text="titled", value=4, variable=self.scale_option
+        )
         button.grid(row=0, column=3, sticky="ew")
         self.options.append(button)
 
     def draw_additional_options(self):
         checkbutton = ttk.Checkbutton(
-            self.top, text="Show grid", variable=self.show_grid_var
+            self.top, text="Show grid", variable=self.show_grid
         )
         checkbutton.grid(row=4, column=0, sticky="ew", padx=PADX)
 
         checkbutton = ttk.Checkbutton(
             self.top,
             text="Adjust canvas size to image dimensions",
-            variable=self.adjust_to_dim_var,
+            variable=self.adjust_to_dim,
             command=self.click_adjust_canvas,
         )
         checkbutton.grid(row=5, column=0, sticky="ew", padx=PADX)
 
-        self.show_grid_var.set(1)
-        self.adjust_to_dim_var.set(0)
-
     def draw_buttons(self):
         frame = ttk.Frame(self.top)
         frame.grid(row=6, column=0, pady=5, sticky="ew")
@@ -142,13 +137,13 @@ class CanvasBackgroundDialog(Dialog):
             ),
         )
         if filename:
-            self.file_name.set(filename)
-            width, height = 250, 135
-            img = Image.open(filename)
-            img = img.resize((width, height), Image.ANTIALIAS)
-            tk_img = ImageTk.PhotoImage(img)
-            self.image_label.config(image=tk_img, width=width)
-            self.image_label.image = tk_img
+            self.filename.set(filename)
+            self.draw_preview()
+
+    def draw_preview(self):
+        image = Images.create(self.filename.get(), 250, 135)
+        self.image_label.config(image=image)
+        self.image_label.image = image
 
     def click_clear(self):
         """
@@ -157,218 +152,47 @@ class CanvasBackgroundDialog(Dialog):
         :return: nothing
         """
         # delete entry
-        self.file_name.set("")
+        self.filename.set("")
         # delete display image
         self.image_label.config(image="", width=32)
+        self.image_label.image = None
 
     def click_adjust_canvas(self):
         # deselect all radio buttons and grey them out
-        if self.adjust_to_dim_var.get() == 1:
-            self.radiovar.set(0)
+        if self.adjust_to_dim.get():
+            self.scale_option.set(0)
             for option in self.options:
                 option.config(state=tk.DISABLED)
         # turn back the radio button to active state so that user can choose again
-        elif self.adjust_to_dim_var.get() == 0:
-            self.radiovar.set(1)
+        else:
+            self.scale_option.set(1)
             for option in self.options:
                 option.config(state=tk.NORMAL)
-        else:
-            logging.error("canvasbackground.py adjust_canvas_size invalid value")
-
-    def delete_canvas_components(self, tag_list):
-        """
-        delete canvas items whose tag is in the tag list
-
-        :param list[string] tag_list: list of tags
-        :return: nothing
-        """
-        for tag in tag_list:
-            for i in self.canvas.find_withtag(tag):
-                self.canvas.delete(i)
-
-    def get_canvas_width_and_height(self):
-        """
-        retrieve canvas width and height in pixels
-
-        :return: nothing
-        """
-        canvas = self.app.canvas
-        grid = canvas.find_withtag("rectangle")[0]
-        x0, y0, x1, y1 = canvas.coords(grid)
-        canvas_w = abs(x0 - x1)
-        canvas_h = abs(y0 - y1)
-        return canvas_w, canvas_h
-
-    def determine_cropped_image_dimension(self):
-        """
-        determine the dimension of the image after being cropped
-
-        :return: nothing
-        """
-        return
-
-    def upper_left(self, img):
-        tk_img = ImageTk.PhotoImage(img)
-
-        # crop image if it is bigger than canvas
-        canvas_w, canvas_h = self.get_canvas_width_and_height()
-
-        cropx = img_w = tk_img.width()
-        cropy = img_h = tk_img.height()
-
-        if img_w > canvas_w:
-            cropx -= img_w - canvas_w
-        if img_h > canvas_h:
-            cropy -= img_h - canvas_h
-        cropped = img.crop((0, 0, cropx, cropy))
-        cropped_tk = ImageTk.PhotoImage(cropped)
-
-        # place left corner of image to the left corner of the canvas
-        self.app.croppedwallpaper = cropped_tk
-
-        self.delete_canvas_components(["wallpaper"])
-        # self.delete_previous_wallpaper()
-
-        wid = self.canvas.create_image(
-            (cropx / 2, cropy / 2), image=cropped_tk, tags="wallpaper"
-        )
-        self.app.wallpaper_id = wid
-
-    def center(self, img):
-        """
-        place the image at the center of canvas
-
-        :param Image img: image object
-        :return: nothing
-        """
-        tk_img = ImageTk.PhotoImage(img)
-        canvas_w, canvas_h = self.get_canvas_width_and_height()
-
-        cropx = img_w = tk_img.width()
-        cropy = img_h = tk_img.height()
-
-        # dimension of the cropped image
-        if img_w > canvas_w:
-            cropx -= img_w - canvas_w
-        if img_h > canvas_h:
-            cropy -= img_h - canvas_h
-
-        x0 = (img_w - cropx) / 2
-        y0 = (img_h - cropy) / 2
-        x1 = x0 + cropx
-        y1 = y0 + cropy
-        cropped = img.crop((x0, y0, x1, y1))
-        cropped_tk = ImageTk.PhotoImage(cropped)
-
-        # place the center of the image at the center of the canvas
-        self.app.croppedwallpaper = cropped_tk
-        self.delete_canvas_components(["wallpaper"])
-        # self.delete_previous_wallpaper()
-        wid = self.canvas.create_image(
-            (canvas_w / 2, canvas_h / 2), image=cropped_tk, tags="wallpaper"
-        )
-        self.app.wallpaper_id = wid
-
-    def scaled(self, img):
-        """
-        scale image based on canvas dimension
-
-        :param Image img: image object
-        :return: nothing
-        """
-        canvas_w, canvas_h = self.get_canvas_width_and_height()
-        resized_image = img.resize((int(canvas_w), int(canvas_h)), Image.ANTIALIAS)
-        image_tk = ImageTk.PhotoImage(resized_image)
-        self.app.croppedwallpaper = image_tk
-
-        self.delete_canvas_components(["wallpaper"])
-        # self.delete_previous_wallpaper()
-
-        wid = self.canvas.create_image(
-            (canvas_w / 2, canvas_h / 2), image=image_tk, tags="wallpaper"
-        )
-        self.app.wallpaper_id = wid
-
-    def tiled(self, img):
-        return
-
-    def draw_new_canvas(self, canvas_width, canvas_height):
-        """
-        delete the old canvas and draw a new one
-
-        :param int canvas_width: canvas width in pixel
-        :param int canvas_height: canvas height in pixel
-        :return:
-        """
-        self.delete_canvas_components(["rectangle", "gridline"])
-        self.canvas.draw_grid(canvas_width, canvas_height)
-
-    def canvas_to_image_dimension(self, img):
-        image_tk = ImageTk.PhotoImage(img)
-        img_w = image_tk.width()
-        img_h = image_tk.height()
-        self.delete_canvas_components(["wallpaper"])
-        self.draw_new_canvas(img_w, img_h)
-        wid = self.canvas.create_image((img_w / 2, img_h / 2), image=image_tk)
-        self.app.croppedwallpaper = image_tk
-        self.app.wallpaper_id = wid
-
-    def show_grid(self):
-        """
-
-        :return: nothing
-        """
-        self.app.adjust_to_dim_var.set(self.adjust_to_dim_var.get())
-
-        if self.show_grid_var.get() == 0:
-            for i in self.canvas.find_withtag("gridline"):
-                self.canvas.itemconfig(i, state=tk.HIDDEN)
-        elif self.show_grid_var.get() == 1:
-            for i in self.canvas.find_withtag("gridline"):
-                self.canvas.itemconfig(i, state=tk.NORMAL)
-                self.canvas.lift(i)
-        else:
-            logging.error("canvasbackground.py show_grid invalid value")
-
-    def save_wallpaper_options(self):
-        self.app.radiovar.set(self.radiovar.get())
-        self.app.show_grid_var.set(self.show_grid_var.get())
-        self.app.adjust_to_dim_var.set(self.adjust_to_dim_var.get())
 
     def click_apply(self):
-        filename = self.file_name.get()
+        self.canvas.scale_option.set(self.scale_option.get())
+        self.canvas.show_grid.set(self.show_grid.get())
+        self.canvas.adjust_to_dim.set(self.adjust_to_dim.get())
+        self.canvas.update_grid()
+
+        filename = self.filename.get()
         if not filename:
-            self.delete_canvas_components(["wallpaper"])
+            self.canvas.delete(self.canvas.wallpaper_id)
+            self.canvas.wallpaper = None
+            self.canvas.wallpaper_file = None
             self.destroy()
-            self.app.current_wallpaper = None
-            self.save_wallpaper_options()
             return
 
         try:
             img = Image.open(filename)
-            self.app.current_wallpaper = img
+            self.canvas.wallpaper = img
+            self.canvas.wallpaper_file = filename
+            self.canvas.redraw()
         except FileNotFoundError:
             logging.error("invalid background: %s", filename)
-            if self.app.wallpaper_id:
-                self.canvas.delete(self.app.wallpaper_id)
-            self.destroy()
-            return
+            if self.canvas.wallpaper_id:
+                self.canvas.delete(self.canvas.wallpaper_id)
+                self.canvas.wallpaper_id = None
+                self.canvas.wallpaper_file = None
 
-        self.app.adjust_to_dim_var.set(self.adjust_to_dim_var.get())
-        if self.adjust_to_dim_var.get() == 0:
-            self.app.radiovar.set(self.radiovar.get())
-            option = ScaleOption(self.radiovar.get())
-            if option == ScaleOption.UPPER_LEFT:
-                self.upper_left(img)
-            elif option == ScaleOption.CENTERED:
-                self.center(img)
-            elif option == ScaleOption.SCALED:
-                self.scaled(img)
-            elif option == ScaleOption.TILED:
-                print("not implemented yet")
-
-        elif self.adjust_to_dim_var.get() == 1:
-            self.canvas_to_image_dimension(img)
-
-        self.show_grid()
         self.destroy()
diff --git a/coretk/coretk/dialogs/canvassizeandscale.py b/coretk/coretk/dialogs/canvassizeandscale.py
index 09132aef..3a72389d 100644
--- a/coretk/coretk/dialogs/canvassizeandscale.py
+++ b/coretk/coretk/dialogs/canvassizeandscale.py
@@ -4,12 +4,9 @@ size and scale
 import tkinter as tk
 from tkinter import font, ttk
 
-from coretk.dialogs.canvasbackground import ScaleOption
 from coretk.dialogs.dialog import Dialog
 
-DRAW_OBJECT_TAGS = ["edge", "node", "nodename", "linkinfo", "antenna"]
-FRAME_BAD = 5
-PAD = (0, 0, 5, 0)
+FRAME_PAD = 5
 PADX = 5
 
 
@@ -21,13 +18,13 @@ class SizeAndScaleDialog(Dialog):
         :param app: main application
         """
         super().__init__(master, app, "Canvas Size and Scale", modal=True)
-        self.meter_per_pixel = self.app.canvas.meters_per_pixel
+        self.canvas = self.app.canvas
+        self.meter_per_pixel = self.canvas.meters_per_pixel
         self.section_font = font.Font(weight="bold")
 
         # get current canvas dimensions
-        canvas = self.app.canvas
-        plot = canvas.find_withtag("rectangle")
-        x0, y0, x1, y1 = canvas.bbox(plot[0])
+        plot = self.canvas.find_withtag("rectangle")
+        x0, y0, x1, y1 = self.canvas.bbox(plot[0])
         width = abs(x0 - x1) - 2
         height = abs(y0 - y1) - 2
         self.pixel_width = tk.IntVar(value=width)
@@ -52,7 +49,7 @@ class SizeAndScaleDialog(Dialog):
         self.draw_buttons()
 
     def draw_size(self):
-        label_frame = ttk.Labelframe(self.top, text="Size", padding=FRAME_BAD)
+        label_frame = ttk.Labelframe(self.top, text="Size", padding=FRAME_PAD)
         label_frame.grid(sticky="ew")
         label_frame.columnconfigure(0, weight=1)
 
@@ -89,7 +86,7 @@ class SizeAndScaleDialog(Dialog):
         label.grid(row=0, column=4, sticky="w")
 
     def draw_scale(self):
-        label_frame = ttk.Labelframe(self.top, text="Scale", padding=FRAME_BAD)
+        label_frame = ttk.Labelframe(self.top, text="Scale", padding=FRAME_PAD)
         label_frame.grid(sticky="ew")
         label_frame.columnconfigure(0, weight=1)
 
@@ -105,7 +102,7 @@ class SizeAndScaleDialog(Dialog):
 
     def draw_reference_point(self):
         label_frame = ttk.Labelframe(
-            self.top, text="Reference Point", padding=FRAME_BAD
+            self.top, text="Reference Point", padding=FRAME_PAD
         )
         label_frame.grid(sticky="ew")
         label_frame.columnconfigure(0, weight=1)
@@ -122,14 +119,12 @@ class SizeAndScaleDialog(Dialog):
 
         label = ttk.Label(frame, text="X")
         label.grid(row=0, column=0, sticky="w", padx=PADX)
-        x_var = tk.StringVar(value=0)
-        entry = ttk.Entry(frame, textvariable=x_var)
+        entry = ttk.Entry(frame, textvariable=self.x)
         entry.grid(row=0, column=1, sticky="ew", padx=PADX)
 
         label = ttk.Label(frame, text="Y")
         label.grid(row=0, column=2, sticky="w", padx=PADX)
-        y_var = tk.StringVar(value=0)
-        entry = ttk.Entry(frame, textvariable=y_var)
+        entry = ttk.Entry(frame, textvariable=self.y)
         entry.grid(row=0, column=3, sticky="ew", padx=PADX)
 
         label = ttk.Label(label_frame, text="Translates To")
@@ -174,47 +169,11 @@ class SizeAndScaleDialog(Dialog):
         button = ttk.Button(frame, text="Cancel", command=self.destroy)
         button.grid(row=0, column=1, sticky="ew")
 
-    def redraw_grid(self):
-        """
-        redraw grid with new dimension
-
-        :return: nothing
-        """
-        width, height = self.pixel_width.get(), self.pixel_height.get()
-
-        canvas = self.app.canvas
-        canvas.config(scrollregion=(0, 0, width + 200, height + 200))
-
-        # delete old plot and redraw
-        for i in canvas.find_withtag("gridline"):
-            canvas.delete(i)
-        for i in canvas.find_withtag("rectangle"):
-            canvas.delete(i)
-
-        canvas.draw_grid(width=width, height=height)
-        # lift anything that is drawn on the plot before
-        for tag in DRAW_OBJECT_TAGS:
-            for i in canvas.find_withtag(tag):
-                canvas.lift(i)
-
     def click_apply(self):
         meter_per_pixel = float(self.scale.get()) / 100
-        self.app.canvas.meters_per_pixel = meter_per_pixel
-        self.redraw_grid()
-        # if there is a current wallpaper showing, redraw it based on current wallpaper options
-        wallpaper_tool = self.app.set_wallpaper
-        current_wallpaper = self.app.current_wallpaper
-        if current_wallpaper:
-            if self.app.adjust_to_dim_var.get() == 0:
-                if self.app.radiovar.get() == ScaleOption.UPPER_LEFT.value:
-                    wallpaper_tool.upper_left(current_wallpaper)
-                elif self.app.radiovar.get() == ScaleOption.CENTERED.value:
-                    wallpaper_tool.center(current_wallpaper)
-                elif self.app.radiovar.get() == ScaleOption.SCALED.value:
-                    wallpaper_tool.scaled(current_wallpaper)
-                elif self.app.radiovar.get() == ScaleOption.TILED.value:
-                    print("not implemented")
-            elif self.app.adjust_to_dim_var.get() == 1:
-                wallpaper_tool.canvas_to_image_dimension(current_wallpaper)
-            wallpaper_tool.show_grid()
+        width, height = self.pixel_width.get(), self.pixel_height.get()
+        self.canvas.meters_per_pixel = meter_per_pixel
+        self.canvas.redraw_grid(width, height)
+        if self.canvas.wallpaper:
+            self.canvas.redraw()
         self.destroy()
diff --git a/coretk/coretk/dialogs/customnodes.py b/coretk/coretk/dialogs/customnodes.py
index 154b7868..f427f08b 100644
--- a/coretk/coretk/dialogs/customnodes.py
+++ b/coretk/coretk/dialogs/customnodes.py
@@ -35,7 +35,7 @@ class ServicesSelectDialog(Dialog):
         self.groups.listbox.selection_set(0)
 
         self.services = CheckboxList(
-            frame, text="Services", clicked=self.service_clicked
+            frame, self.app, text="Services", clicked=self.service_clicked
         )
         self.services.grid(row=0, column=1, sticky="nsew")
 
diff --git a/coretk/coretk/dialogs/emaneconfig.py b/coretk/coretk/dialogs/emaneconfig.py
index 181e1264..d64e9089 100644
--- a/coretk/coretk/dialogs/emaneconfig.py
+++ b/coretk/coretk/dialogs/emaneconfig.py
@@ -93,7 +93,7 @@ class EmaneConfiguration(Dialog):
         self.emane_dialog.top.columnconfigure(0, weight=1)
         self.emane_dialog.top.rowconfigure(0, weight=1)
         self.emane_config_frame = ConfigFrame(
-            self.emane_dialog.top, config=self.options
+            self.emane_dialog.top, self.app, config=self.options
         )
         self.emane_config_frame.draw_config()
         self.emane_config_frame.grid(sticky="nsew")
@@ -167,7 +167,7 @@ class EmaneConfiguration(Dialog):
 
         self.model_options = response.config
         self.model_config_frame = ConfigFrame(
-            self.emane_model_dialog.top, config=self.model_options
+            self.emane_model_dialog.top, self.app, config=self.model_options
         )
         self.model_config_frame.grid(sticky="nsew")
         self.model_config_frame.draw_config()
diff --git a/coretk/coretk/dialogs/nodeservice.py b/coretk/coretk/dialogs/nodeservice.py
index ce5a4715..9ced9205 100644
--- a/coretk/coretk/dialogs/nodeservice.py
+++ b/coretk/coretk/dialogs/nodeservice.py
@@ -38,7 +38,7 @@ class NodeService(Dialog):
         self.groups.listbox.selection_set(0)
 
         self.services = CheckboxList(
-            frame, text="Services", clicked=self.service_clicked
+            frame, self.app, text="Services", clicked=self.service_clicked
         )
         self.services.grid(row=0, column=1, sticky="nsew")
 
diff --git a/coretk/coretk/dialogs/preferences.py b/coretk/coretk/dialogs/preferences.py
index 0c426d3c..148cb6bb 100644
--- a/coretk/coretk/dialogs/preferences.py
+++ b/coretk/coretk/dialogs/preferences.py
@@ -1,3 +1,4 @@
+import logging
 import tkinter as tk
 from tkinter import ttk
 
@@ -10,41 +11,52 @@ class PreferencesDialog(Dialog):
         super().__init__(master, app, "Preferences", modal=True)
         preferences = self.app.config["preferences"]
         self.editor = tk.StringVar(value=preferences["editor"])
+        self.theme = tk.StringVar(value=preferences["theme"])
         self.terminal = tk.StringVar(value=preferences["terminal"])
         self.gui3d = tk.StringVar(value=preferences["gui3d"])
         self.draw()
 
     def draw(self):
         self.top.columnconfigure(0, weight=1)
-        self.draw_programs()
+        self.draw_preferences()
         self.draw_buttons()
 
-    def draw_programs(self):
-        frame = ttk.LabelFrame(self.top, text="Programs")
+    def draw_preferences(self):
+        frame = ttk.LabelFrame(self.top, text="Preferences")
         frame.grid(sticky="ew", pady=2)
         frame.columnconfigure(1, weight=1)
 
-        label = ttk.Label(frame, text="Editor")
+        label = ttk.Label(frame, text="Theme")
         label.grid(row=0, column=0, pady=2, padx=2, sticky="w")
+        themes = self.app.style.theme_names()
+        combobox = ttk.Combobox(
+            frame, textvariable=self.theme, values=themes, state="readonly"
+        )
+        combobox.set(self.theme.get())
+        combobox.grid(row=0, column=1, sticky="ew")
+        combobox.bind("<<ComboboxSelected>>", self.theme_change)
+
+        label = ttk.Label(frame, text="Editor")
+        label.grid(row=1, column=0, pady=2, padx=2, sticky="w")
         combobox = ttk.Combobox(
             frame, textvariable=self.editor, values=appconfig.EDITORS, state="readonly"
         )
-        combobox.grid(row=0, column=1, sticky="ew")
+        combobox.grid(row=1, column=1, sticky="ew")
 
         label = ttk.Label(frame, text="Terminal")
-        label.grid(row=1, column=0, pady=2, padx=2, sticky="w")
+        label.grid(row=2, column=0, pady=2, padx=2, sticky="w")
         combobox = ttk.Combobox(
             frame,
             textvariable=self.terminal,
             values=appconfig.TERMINALS,
             state="readonly",
         )
-        combobox.grid(row=1, column=1, sticky="ew")
+        combobox.grid(row=2, column=1, sticky="ew")
 
         label = ttk.Label(frame, text="3D GUI")
-        label.grid(row=2, column=0, pady=2, padx=2, sticky="w")
+        label.grid(row=3, column=0, pady=2, padx=2, sticky="w")
         entry = ttk.Entry(frame, textvariable=self.gui3d)
-        entry.grid(row=2, column=1, sticky="ew")
+        entry.grid(row=3, column=1, sticky="ew")
 
     def draw_buttons(self):
         frame = ttk.Frame(self.top)
@@ -58,10 +70,16 @@ class PreferencesDialog(Dialog):
         button = ttk.Button(frame, text="Cancel", command=self.destroy)
         button.grid(row=0, column=1, sticky="ew")
 
+    def theme_change(self, event):
+        theme = self.theme.get()
+        logging.info("changing theme: %s", theme)
+        self.app.style.theme_use(theme)
+
     def click_save(self):
         preferences = self.app.config["preferences"]
         preferences["terminal"] = self.terminal.get()
         preferences["editor"] = self.editor.get()
         preferences["gui3d"] = self.gui3d.get()
+        preferences["theme"] = self.theme.get()
         self.app.save_config()
         self.destroy()
diff --git a/coretk/coretk/dialogs/sessionoptions.py b/coretk/coretk/dialogs/sessionoptions.py
index 8cd7ad68..b2666015 100644
--- a/coretk/coretk/dialogs/sessionoptions.py
+++ b/coretk/coretk/dialogs/sessionoptions.py
@@ -22,7 +22,7 @@ class SessionOptionsDialog(Dialog):
         response = self.app.core.client.get_session_options(session_id)
         logging.info("session options: %s", response)
 
-        self.config_frame = ConfigFrame(self.top, config=response.config)
+        self.config_frame = ConfigFrame(self.top, self.app, config=response.config)
         self.config_frame.draw_config()
         self.config_frame.grid(sticky="nsew")
 
diff --git a/coretk/coretk/graph.py b/coretk/coretk/graph.py
index 5cdd2eec..e5bab65b 100644
--- a/coretk/coretk/graph.py
+++ b/coretk/coretk/graph.py
@@ -2,6 +2,8 @@ import enum
 import logging
 import tkinter as tk
 
+from PIL import ImageTk
+
 from core.api.grpc import core_pb2
 from coretk.canvasaction import CanvasAction
 from coretk.canvastooltip import CanvasTooltip
@@ -21,6 +23,14 @@ class GraphMode(enum.Enum):
     OTHER = 4
 
 
+class ScaleOption(enum.Enum):
+    NONE = 0
+    UPPER_LEFT = 1
+    CENTERED = 2
+    SCALED = 3
+    TILED = 4
+
+
 CORE_NODES = ["router"]
 CORE_WIRED_NETWORK_NODES = []
 CORE_WIRELESS_NODE = ["wlan"]
@@ -43,11 +53,8 @@ class CanvasGraph(tk.Canvas):
         self.drawing_edge = None
         self.grid = None
         self.meters_per_pixel = 1.5
-
         self.canvas_management = CanvasComponentManagement(self, core)
-
         self.canvas_action = CanvasAction(master, self)
-
         self.setup_menus()
         self.setup_bindings()
         self.draw_grid()
@@ -57,6 +64,15 @@ class CanvasGraph(tk.Canvas):
         self.wireless_draw = WirelessConnection(self, core)
         self.is_node_context_opened = False
 
+        # background related
+        self.wallpaper_id = None
+        self.wallpaper = None
+        self.wallpaper_drawn = None
+        self.wallpaper_file = ""
+        self.scale_option = tk.IntVar(value=1)
+        self.show_grid = tk.BooleanVar(value=True)
+        self.adjust_to_dim = tk.BooleanVar(value=False)
+
     def setup_menus(self):
         self.node_context = tk.Menu(self.master)
         self.node_context.add_command(
@@ -95,8 +111,6 @@ class CanvasGraph(tk.Canvas):
         self.drawing_edge = None
         self.draw_existing_component(session)
 
-        # self.grpc_manager.wlanconfig_management.load_wlan_configurations(self.core_grpc)
-
     def setup_bindings(self):
         """
         Bind any mouse events or hot keys to the matching action
@@ -128,11 +142,12 @@ class CanvasGraph(tk.Canvas):
             width=1,
             tags="rectangle",
         )
-        self.tag_lower(self.grid)
         for i in range(0, width, 27):
             self.create_line(i, 0, i, height, dash=(2, 4), tags="gridline")
         for i in range(0, height, 27):
             self.create_line(0, i, width, i, dash=(2, 4), tags="gridline")
+        self.tag_lower("gridline")
+        self.tag_lower(self.grid)
 
     def draw_existing_component(self, session):
         """
@@ -224,9 +239,8 @@ class CanvasGraph(tk.Canvas):
                 if2
             )
 
-        # lift the nodes so they on top of the links
-        for i in self.find_withtag("node"):
-            self.lift(i)
+        # raise the nodes so they on top of the links
+        self.tag_raise("node")
 
     def canvas_xy(self, event):
         """
@@ -422,6 +436,132 @@ class CanvasGraph(tk.Canvas):
             self.core.add_graph_node(self.core.session_id, node.id, x, y, node_name)
             return node
 
+    def width_and_height(self):
+        """
+        retrieve canvas width and height in pixels
+
+        :return: nothing
+        """
+        grid = self.find_withtag("rectangle")[0]
+        x0, y0, x1, y1 = self.coords(grid)
+        canvas_w = abs(x0 - x1)
+        canvas_h = abs(y0 - y1)
+        return canvas_w, canvas_h
+
+    def wallpaper_upper_left(self):
+        tk_img = ImageTk.PhotoImage(self.wallpaper)
+        # crop image if it is bigger than canvas
+        canvas_w, canvas_h = self.width_and_height()
+        cropx = img_w = tk_img.width()
+        cropy = img_h = tk_img.height()
+        if img_w > canvas_w:
+            cropx -= img_w - canvas_w
+        if img_h > canvas_h:
+            cropy -= img_h - canvas_h
+        cropped = self.wallpaper.crop((0, 0, cropx, cropy))
+        cropped_tk = ImageTk.PhotoImage(cropped)
+        self.delete(self.wallpaper_id)
+        # place left corner of image to the left corner of the canvas
+        self.wallpaper_id = self.create_image(
+            (cropx / 2, cropy / 2), image=cropped_tk, tags="wallpaper"
+        )
+        self.wallpaper_drawn = cropped_tk
+
+    def wallpaper_center(self):
+        """
+        place the image at the center of canvas
+
+        :param Image img: image object
+        :return: nothing
+        """
+        tk_img = ImageTk.PhotoImage(self.wallpaper)
+        canvas_w, canvas_h = self.width_and_height()
+        cropx = img_w = tk_img.width()
+        cropy = img_h = tk_img.height()
+        # dimension of the cropped image
+        if img_w > canvas_w:
+            cropx -= img_w - canvas_w
+        if img_h > canvas_h:
+            cropy -= img_h - canvas_h
+        x0 = (img_w - cropx) / 2
+        y0 = (img_h - cropy) / 2
+        x1 = x0 + cropx
+        y1 = y0 + cropy
+        cropped = self.wallpaper.crop((x0, y0, x1, y1))
+        cropped_tk = ImageTk.PhotoImage(cropped)
+        # place the center of the image at the center of the canvas
+        self.delete(self.wallpaper_id)
+        self.wallpaper_id = self.create_image(
+            (canvas_w / 2, canvas_h / 2), image=cropped_tk, tags="wallpaper"
+        )
+        self.wallpaper_drawn = cropped_tk
+
+    def wallpaper_scaled(self):
+        """
+        scale image based on canvas dimension
+
+        :param Image img: image object
+        :return: nothing
+        """
+        canvas_w, canvas_h = self.width_and_height()
+        image = Images.create(self.wallpaper_file, int(canvas_w), int(canvas_h))
+        self.delete(self.wallpaper_id)
+        self.wallpaper_id = self.create_image(
+            (canvas_w / 2, canvas_h / 2), image=image, tags="wallpaper"
+        )
+        self.wallpaper_drawn = image
+
+    def resize_to_wallpaper(self):
+        image_tk = ImageTk.PhotoImage(self.wallpaper)
+        img_w = image_tk.width()
+        img_h = image_tk.height()
+        self.delete(self.wallpaper_id)
+        self.delete("rectangle")
+        self.delete("gridline")
+        self.draw_grid(img_w, img_h)
+        self.wallpaper_id = self.create_image((img_w / 2, img_h / 2), image=image_tk)
+        self.wallpaper_drawn = image_tk
+
+    def redraw_grid(self, width, height):
+        """
+        redraw grid with new dimension
+
+        :return: nothing
+        """
+        self.config(scrollregion=(0, 0, width + 200, height + 200))
+
+        # delete previous grid
+        self.delete("rectangle")
+        self.delete("gridline")
+
+        # redraw
+        self.draw_grid(width=width, height=height)
+
+        # hide/show grid
+        self.update_grid()
+
+    def redraw(self):
+        if self.adjust_to_dim.get():
+            self.resize_to_wallpaper()
+        else:
+            option = ScaleOption(self.scale_option.get())
+            if option == ScaleOption.UPPER_LEFT:
+                self.wallpaper_upper_left()
+            elif option == ScaleOption.CENTERED:
+                self.wallpaper_center()
+            elif option == ScaleOption.SCALED:
+                self.wallpaper_scaled()
+            elif option == ScaleOption.TILED:
+                logging.warning("tiled background not implemented yet")
+
+    def update_grid(self):
+        logging.info("updating grid show: %s", self.show_grid.get())
+        if self.show_grid.get():
+            self.itemconfig("gridline", state=tk.NORMAL)
+            self.tag_raise("gridline")
+        else:
+            self.itemconfig("gridline", state=tk.HIDDEN)
+
 
 class CanvasEdge:
     """
@@ -465,8 +605,6 @@ class CanvasEdge:
         self.link_info = None
         self.throughput = None
         self.wired = is_wired
-        # TODO resolve this
-        # self.canvas.tag_lower(self.id)
 
     def complete(self, dst, x, y):
         self.dst = dst
@@ -474,8 +612,8 @@ class CanvasEdge:
         x1, y1, _, _ = self.canvas.coords(self.id)
         self.canvas.coords(self.id, x1, y1, x, y)
         self.canvas.helper.draw_wireless_case(self.src, self.dst, self)
-        self.canvas.lift(self.src)
-        self.canvas.lift(self.dst)
+        self.canvas.tag_raise(self.src)
+        self.canvas.tag_raise(self.dst)
 
     def delete(self):
         self.canvas.delete(self.id)
diff --git a/coretk/coretk/icons/emane.gif b/coretk/coretk/icons/emane.gif
index 8a3d3850..0531a932 100644
Binary files a/coretk/coretk/icons/emane.gif and b/coretk/coretk/icons/emane.gif differ
diff --git a/coretk/coretk/icons/wlan.gif b/coretk/coretk/icons/wlan.gif
index d72fe9c3..56618576 100644
Binary files a/coretk/coretk/icons/wlan.gif and b/coretk/coretk/icons/wlan.gif differ
diff --git a/coretk/coretk/menuaction.py b/coretk/coretk/menuaction.py
index 98b3d254..b47c6ef2 100644
--- a/coretk/coretk/menuaction.py
+++ b/coretk/coretk/menuaction.py
@@ -73,7 +73,6 @@ class MenuAction:
 
     def file_open_xml(self, event=None):
         logging.info("menuaction.py file_open_xml()")
-        self.app.is_open_xml = True
         file_path = filedialog.askopenfilename(
             initialdir=str(XML_PATH),
             title="Open",
diff --git a/coretk/coretk/themes.py b/coretk/coretk/themes.py
index b661b644..f6dced19 100644
--- a/coretk/coretk/themes.py
+++ b/coretk/coretk/themes.py
@@ -1,3 +1,4 @@
+import logging
 import tkinter as tk
 
 DARK = "black"
@@ -6,6 +7,7 @@ DARK = "black"
 class Styles:
     tooltip = "Tooltip.TLabel"
     tooltip_frame = "Tooltip.TFrame"
+    service_checkbutton = "Service.TCheckbutton"
 
 
 class Colors:
@@ -20,6 +22,7 @@ class Colors:
     selectfg = "#ffffff"
     white = "white"
     black = "black"
+    listboxbg = "#f2f1f0"
 
 
 def load(style):
@@ -86,6 +89,7 @@ def load(style):
                     "padding": (2, 0),
                 }
             },
+            "TLabelframe": {"configure": {"relief": tk.GROOVE}},
             "TNotebook.Tab": {
                 "configure": {"padding": (6, 2, 6, 2)},
                 "map": {"background": [("selected", Colors.lighter)]},
@@ -105,13 +109,18 @@ def load(style):
                 "configure": {"justify": tk.LEFT, "relief": tk.SOLID, "borderwidth": 0}
             },
             Styles.tooltip_frame: {"configure": {}},
+            Styles.service_checkbutton: {
+                "configure": {
+                    "background": Colors.listboxbg,
+                    "foreground": Colors.black,
+                }
+            },
         },
     )
 
 
-def update_toplevel(style, event):
-    if not isinstance(event.widget, tk.Toplevel):
-        return
+def update_bg(style, event):
+    logging.info("updating background: %s", event.widget)
     bg = style.lookup(".", "background")
     event.widget.config(background=bg)
 
diff --git a/coretk/coretk/widgets.py b/coretk/coretk/widgets.py
index 87651701..e825fdb4 100644
--- a/coretk/coretk/widgets.py
+++ b/coretk/coretk/widgets.py
@@ -18,11 +18,13 @@ INT_TYPES = {
 
 
 class FrameScroll(ttk.LabelFrame):
-    def __init__(self, master=None, _cls=tk.Frame, **kw):
+    def __init__(self, master, app, _cls=ttk.Frame, **kw):
         super().__init__(master, **kw)
+        self.app = app
         self.rowconfigure(0, weight=1)
         self.columnconfigure(0, weight=1)
-        self.canvas = tk.Canvas(self, highlightthickness=0)
+        bg = self.app.style.lookup(".", "background")
+        self.canvas = tk.Canvas(self, highlightthickness=0, background=bg)
         self.canvas.grid(row=0, sticky="nsew", padx=2, pady=2)
         self.canvas.columnconfigure(0, weight=1)
         self.canvas.rowconfigure(0, weight=1)
@@ -54,8 +56,8 @@ class FrameScroll(ttk.LabelFrame):
 
 
 class ConfigFrame(FrameScroll):
-    def __init__(self, master=None, config=None, **kw):
-        super().__init__(master, ttk.Notebook, **kw)
+    def __init__(self, master, app, config, **kw):
+        super().__init__(master, app, ttk.Notebook, **kw)
         self.config = config
         self.values = {}
 
@@ -136,13 +138,14 @@ class ListboxScroll(ttk.LabelFrame):
         self.listbox = tk.Listbox(
             self, selectmode=tk.SINGLE, yscrollcommand=self.scrollbar.set
         )
+        logging.info("listbox background: %s", self.listbox.cget("background"))
         self.listbox.grid(row=0, column=0, sticky="nsew")
         self.scrollbar.config(command=self.listbox.yview)
 
 
 class CheckboxList(FrameScroll):
-    def __init__(self, master=None, clicked=None, **kw):
-        super().__init__(master, **kw)
+    def __init__(self, master, app, clicked=None, **kw):
+        super().__init__(master, app, **kw)
         self.clicked = clicked
         self.frame.columnconfigure(0, weight=1)