If there are a few icons on your iPhone that you just dont like and would rather change to something a little more pleasing. There is a method you can use that doesnt require you to jailbreak your iPhone.
This neat little mod will work on both mac and Windows machines using iPhone Explorer (download it from the link). This method will only work for the app your have purchased in the app store. You cannot change the icons of the app loaded onto your iPhone by Apple.
1. First open iPhone Explorer and navigate into the app’s folder, located in /Apps/appname.app/appname.app.app (whereappname is the name of the app you want to change and devicename is the name of your device).
2. Within that folder, find the png file that is the icon, named something like icon@2x.png for an iPhone 4, or Icon.png for iPhone 3GS and below. Back that up and replace it with your own icon
3. Make sure the icon is in PNG format and is 114×114 pixels for the iPhone 4, 57×57 for the iPhone 3GS and earlier. After rebooting your phone, you should see the old icon replaced with your new one.
Via Lifehacker