I think Windows 7 Themes are cool.

They are stored in this directory: C:\Users\<username>\AppData\Local\Microsoft\Windows\Themes

Note: <username> is your name or whatever you chose as the Log-In name. Open the directory and you’ll find it.

Here is a Theme Template to get you started. Copy & Paste this into Notepad. Be sure to Save it with a .theme extension!!

via WinCom7: Windows 7 News, Tips, and Security.