This skin from Topdecal on Etsy can give your iPhone 4 the look of a Leica camera. You can choose from a Leica X1, M8, or M9 look for $9.90 each. The skins are precision-cut from vinyl that has a 3-5 years outdoors lifespan. The vinyl skin can be removed without damaging your iPhone and without sticky residue. The skin is thin and it provides scratch-protection for the back of your iPhone.