I have three words for you - So. Much. Fun. I'm doing these for my Monday Night quilt group and the aim is to combine all our Polaroids into a quilt and do something altruistic with it. I'm so making some for me though! I think the proportions we decided on are a bit off though, the top and sides need to be thinner, but that's easily remedied if I can convince the others!
It's a fairly random assortment of fabrics, and there are definitely more than the required one animal in my lot; but I discovered that when thinking about photo-like blocks I tend to choose fabrics with figures or objects in them, and not surprisingly, those turn out to include a fair number of animals! I've seen some lovely polaroids done with just geometric prints, like more regular quilting designs, and I'd like to try that way too.