Simple wallpaper mod to make gnome-panel have a rounded w/ drop-shadow effect.
1. Open the Panel_mod.xcf with GIMP and replace the Background layer with whatever you want as your background and save as an image GNOME would read as a wallpaper.
2. Set the desktop background to the newly saved image.
3. Set the gnome-panel size to 22 and make it fully transparent.
4. Arrange your panel applets so they are inside the black part of the panel.
4a. I suggest putting an application launcher with a blank icon (included) in the right corner so the notification tray doesn't push other applets outside the panel mod.