ThemePark for Mac

From GeekSpiff:

Down with Aqua! 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 create icon sets that can change every icon on your system, even common document icons.

With ThemePark, you can:

• Create guiKits for use with Unsanity's ShapeShifter;
• Create new themes or icon sets using your own graphics;
• Merge your theme with an existing one to use it as a base or to make small tweaks to someone else's theme;
• Quickly preview your theme while you're constructing it;
• Easily find the element you're looking for using ThemePark's smart organization, filtering, and inline hints;
• Save in-progress themes and easily see which areas you've already modified;
• Edit resource files found inside of many applications;