I've mentioned a few times there are 60 levels in the game. There is a reward painting for each and every level in addition to your score. You can share them with your friends if you'd like (there may or may not be a Game Center achievement for sharing). When you do share you'll be sharing something like this:

http://art.pickpawcket.com/cata-lisa

- or -

http://art.pickpawcket.com/the-persistence-of-cat-naps/