Mac OS X: How to change icon

To change an item's icon to another one

1. Select the volume, application, folder, or file whose icon you want to stamp onto another, just click the icon to select it.
2. From the File menu, choose Get Info or press Command-I to open the Info window.
3. Click the icon in the upper-left corner of the Info window to select it.
4. From the Edit menu, choose Copy or press Command-C.
5. Select the volume, application, folder, or file whose icon you want to replace.
6. From the File menu, choose Get Info or press Command-I.
7. Click the icon in the upper-left corner.
8. From the Edit menu, choose Paste or press Command-V to replace the icon.

Change your user account icon

1. Make sure that you're logged in to the user account whose picture you want to change. From the Apple menu, choose System Preferences.
2. Click Accounts.
3. Click the Picture tab.
4. Click Edit.
5. Drag any image file from your desktop or a Finder window onto the resulting Images window.
6. Use the slider at the bottom of the window to zoom in to your picture. You can also drag the image around in the window to adjust the framing.
7. When satisfied, click Set to make the change.