I don't think ANY sites allow free printing. The National Geographic application on android has some really nice images that maybe you could save to your android device and print. Apple probably have a Nat geo app too.
I got my background from eBay it Wesson only about £6.50 including postage, *looks for a pic with the background visible*
Here we go:
EDIT: water bowl no longer in there, only small hamster sized bowl, and there's less wood in there so he's got more room.