ThemePark lets you give your computer a style of its own.

Use ThemePark to create or modify the way Mac OS X looks, as well as to change the appearance of individual applications. Just draw titlebars, buttons, and other widgets in the graphics editor of your choice, and move them into ThemePark to create a new theme or modify an existing one. Also use ThemePark to safely apply themes to your operating system.

With ThemePark, you can:

Safely apply themes created by other ThemePark users;
Edit the ArtFile, SArtFile and Extras files that underlie the appearance of Mac OS X;
Easily merge multiple themes together to mix and match appearances;
Integrate with Adobe Photoshop™ and Illustrator™ for easy editing;
Convert between the Snow Leopard and the Leopard versions of SArtFile;
Edit many theme images at once for easy modification;