Rainmeter is an awesome little package that you can use to modify your desktop with, heres mine:
I'm currently using a theme called Onmimo 2 that I nabbed from devaintART. There are literally thousands of different themes and plugins that you can add to Rainmeter which gives a lot of customization.
You can get Rainmeter here http://rainmeter.net/RainCMS/
A good place to start looking for Rainmeter themes is to search the devaintART webpage, google works too ;).