I've been wanting to make my own iPhone case since... Well since before I got an iPhone! I finally got round to it, and here's how I did it:
You will need: A clear snap on iPhone case (mine is from Ebay), sturdy decorative paper, craft knife, needle and thread.
1// Draw around your iPhone case on to the back of the paper, don't forget the hole for the camera!
2// Cut out the paper and make sure it fits into the back of the case. You may need to trim it down a bit.
3// You could even just leave it at that, but because I'm a glutton for punishment I decided to cross-stitch a little heart on there. I advice against this if your paper is really thin as it won't take all the stabbing!
4// Carefully snap the case back on to your iPhone with the paper slipped inside, check it fits... and you're done.
The great thing is that because you haven't glued the paper into your case you can change it up as often as you like. Hooray for DIY!
P.S. I posted another iPhone case DIY a while ago - if you fancy making one out of felt, take a look!