You can do a search in android market for live wallpapers. You can also use an alternate market called slideme.
My list of favorite wallpapers:
-Live Aquarium (I love this one but huge battery hog)
-EarthRot Live Wall Paper (absolutely the coolest, makes the SuperAmoled pop with delight)
-VR Tunnel Lite (Comes in as my second favorite, running it now!) (Runs a black screen with grid marks, so the black screen is not too shabby on battery!)
-Bubbles Live Wallpaper (Amazing Amazing Amazing, but HUGE HUGE battery hog, HUGE!)
-Leaf Bubbles Live Wallpaper (same as one above it, but it's leafs, huge battery hog)
-Zoomfield
-Quads
-Physx
-Nexus One Live Wallpaper
All are free. To apply, download, then go to wallpapers, click live wallpapers, and apply through there. Also many of these wallpapers have settings. For example, the earth one, you can change the earth to a soccer ball, you can change the speed of rotation, background, etc.
Enjoy but beware, they use battery!