Wired has a great guide on how to change your iPhone wallpaper. Maybe such a task is simple and self-evident to you, but if not, this tutorial tells you everything you need to know, complete with screen shots. But it goes beyond the basics, showing you how to use as wallpaper your own photos that you've taken, as wall as showing you how to Photoshop your own wallpaper. (As an aside, this how-to is a wiki, meaning that anyone can change it or add to it.