CandyBar allows you to change the system icons in Mac OS X that you normally can't, including including the trash can, volumes, default folder, and more! CandyBar 3 also now includes a full-featured icon organizer (formerly called Pixadex) that acts like an iPhoto for your icons: collect and store your icons in the same application you use to change them!

Version 3.3.3: 
Fixed an issue where icons with 1024x1024 representations would be imported incorrectly
Improved the speed of opening the Quick Look window
Added ability to copy an icon from Get Info and paste it into the Finder properly
  
http://www.panic.com/candybar/