Like many people, I have customized many thing about my OS X setup, not the least of which were app and folder icons. Via programs like CandyBar or LiteIcon, or manually, any and all folder/file/app icons can be changed.
Personally, I like the pure|icns set from Interfacelift. However, there is a problem when programs update -- in my case, Dropbox -- and change their icons back to a boring old Leopard blue. To return my custom icons, I wrote an AppleScript. Since this only happens every now and then, I didn't make the script executable; I just call it from Google's quick search box whenever I need it.
At any rate, this script will copy an icon from some location (file, folder, *.icns), and paste it via the Get Info window for any second location (file, folder, app) that you desire. Of course, change the first two POSIX paths to (1) where the icon should come from, and (2) where the icon should go.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20091111215845472