Staring at the same computer screen at work day after day can drive a person batty. Unfortunately, we're stuck in XP land where I work, so theme options are limited.
Here are the 4 extra official Microsoft Windows XP themes I've been able to dig up. I've included them all in a single zip file to at the bottom of this post. Simply download the zip, extract everything to c:\windows\resources\themes then double-click on the first .theme file, Display Properties will open, hit OK, double-click on the second, hit OK, then the third, hit OK. Now under Display Properties > Appearance > Windows and buttons, you'll now have three more options. Zune, Embedded and Royale with two sub color schemes.
You can download all four themes in the following zip file, installation instructions are included in the readme.txt file: