As we all well know Customize has been released in Cydia. SummerBoard, however, has yet to be released and this is what allows you to put images and video on the iphones springboard background through customize. Click the link to read on and learn how to use the theme browser.
SummerBoard may not yet be here but you can still install themes. When installing themes it will not apply the springboards background, nor will it apply anything to any 3rd party apps you have gotten so this may not be something you want to do. If you do want to install a theme go into theme browser and choose a theme. you can view a preview and its ratings before you download it. Once you have downloaded it go under my themes and select the theme and click apply theme to device.
Customize also allows you to edit the system strings on your phone. Such as changing “slide to unlock” to “do it…”. or changing “slide to power off” to “i will reboot.”
Update: For those confused between summerboard/springboard/customize and dont quite understand- summerboard is (basically) an extension of customize and allows you to put a wallpaper on the springboards homescreen. (it is technically a simplified version of customize) Springboard is what apple calls the home screen and summerboard is the hacked version of the springboard. Without summerboard, you can do nothing to the wallpaper on the home screen. Summerboard installs its own app but it is also integrated into customize. For any more questions post them below and i will do my best to answer!