Is there any way to copy a new graphic used for an existing device without having to recreate the device from scratch?  I know when you press delete for a button, it asks if you want to delete everything or just certain parts.  I can't seem to find a way to copy a new graphic over an existing one.

Okay, I determined that if I go into the "Create and Name Devices" screen, I can drag a new graphic over to the device. Sometimes a dialog box will pop up asking if I want to overwrite the entire device or just the image. That works for some of the devices/actions, but for some of them (especially the ones I'm interested in with macros), the new graphic just pops in and overwrites the entire device. The dialog box asking if you want to overwrite everything or just the image never pops up. I tested it with a couple of them, and two of them are almost entirely identical (one to watch/use Net Radio one to watch/use the Wii) and on one the dialog comes up, the other it doesn't.

Any ideas as to why?

Drag the device graphic as you did but don't drag it on top of the device you want to change. Instead, create a new device graphic. You can then copy the graphic and paste it over the graphic you want to change. Finally, delete the copy you originally dragged into the page. Are the two graphics the same size? If not, delete the first graphic before copying the second one to that device.