http://www.kaleidoscope.net/
Kaleidoscope is the coolest program to make your desktop scheme different. It has been around for the longest time. A lot of people use it, Even some famous people use it like Jenny from Jennicam.com (
http://www.jennicam.org/j2kr/screens/index.html). It is very easy to make schemes of your own. Also I know on the Mac & Wintel that you can change your start up screen. I know it is easy to do so on the mac, but I do not know who to do it with Windows.
Its shareware, but if you like that kind of stuff, Its worth it.