For maybe $.20 or LESS - I made a few fun inserts for the back of my iPhone. I just traced my phone against some snazzy scrapbook paper, cut out...then cut out the hole or shape for the camera lens....this is easiest when using your actual case to trace that little opening. This is super easy, as long as you have a clear(ish) type of case, it'll work! Mine is clear, but with a little tint...and has a quilted look which I actually really like because it gives the paper some dimension & texture.
I made a little template out of clear, thick, plastic tracing sheets, that way I can make a bunch. I LOVE this because I can change them out any day...even coordinate it to my outfit...without breaking the bank buying those super expensive pre-colored/designed cases!