if you want to change the icons in mac OS X, you need to go to finder, then go to the application folder. Right click the app you want the icon to be changed, and click “show package contents”. Then, go to resources, find the icon you want to replace, and move it somewhere else for safe keepings. rename the icon you want to use to the icon you just moved. drag it into the folder, and you got the awesome icon you want.
took me a while to find this out so I thought I would pass the word on!