Winterboard is a free app to be had in Cydia which lets you customise the looks of your jailbroken iPhone in almost anyway you like.
With iPhone Theme Simulator, you can customize the springboard, lockscreen, Status bar, WiFi and battery logos, background, time and date styling, ic
ons for apps and the dotted scroll buttons at the bottom.
The app is currently available for Windows only, but I have been told that a Mac version of the app is currently in final testing stages, and could be out by the end of this week or even earlier.
Download iPhone Theme Simulator for Windows