Here’s a cool link (via Slashdot): Transparent Screen Backgrounds. Take a digital picture of the area behind your monitor, crop and resize it until lies up visually with the area of your computer screen, and set it to your desktop wallpaper. Some of the example are pretty wild.
I’d try it myself, but with my Windows XP dual monitor setup, I get the same wallpaper on both screens. Anybody know of any utilites that allow you have different wallpaper on each screen, like you can with Gnome/KDE?