This is something we as graphic and web designers like to do and it’s quite easy to accomplish. There are two ways to change the icons in Mac OS X; the first is a simple copy and paste method and the second uses a nifty little program called CandyBar.
Copy and Paste Method
A simple way to change the icons in Mac OS X is to create your icon image in a program like Adobe Photoshop, save it somewhere and then go to that location in “Finder”, right click (cmd + click) and “Copy” the icon. Now, go to the folder that uses an icon you want to change, and right click (cmd + click) on the folder to be able to select “Get Info” from the pop up menu. Click the icon at the top left of this window and simply press cmd + v to paste it. Voila, new icon should now be in that top left icon area to show you that you completed the process correctly.
Another way to complete this is to download “CandyBar“. It is a Mac OS X program that makes it quick and easy to change icons on Mac OS X, even application folders which can sometimes refuse to change when using the copy and paste method discussed previously.