You can use Winterboard and some themes to do that. But if you're only interested to change that one image/icon, then just use a app like iFile to search that picture in your iDevice's file system and replace it with another on or edit it with an app, e.g. Photoshop (Touch).
You can also use a desktop PC and an app like DiskAid to search that file on your computer. To have access to your file system you need to install afc2add (until 7.0.x) or Apple File Conduit (7.1.x) on your desired iDevice
The path on my iPhone 4S with iOS7.0.6 is the following:
file:///var/stash/Applications.1cg9zT/MobileSafari.app/
There you have to chose the picture/icon you want to change/edit/exchange
Hope that helps you