One of the things you can change on any stock iPhone or iPad is the wallpaper image that appears on both the Home Screen and Lock Screen. Unfortunately for Apple device users, that’s just about the extent of background image customization on the iPhone and iPad platforms; but it doesn’t have to be.
Assuming you’ve got a jailbroken handset at your disposal, then you can take advantage of a newly released jailbreak tweak called MyWall by iOS developer iOSthemem0d to customize the background of just about any iOS interface you can imagine.