I love my cats, and I take photos of them frequently and with reckless abandon. That said, I'm not entirely sure I need more than one specialized app just for sharing photos of Nibbler and Cinnamon (don't judge me). Regardless, a couple of months after the iOS version of Peterest hit the scene, we now have Petigram. OK, so pet photo apps clearly still need to work on original naming schemes, but we'll ignore that for the moment.
Petigram offers the ability to share photos, follow other users, and post comments. Its main selling point, however, is the built-in photo editing tools that let you add borders, text and other obnoxious graphics. At the moment, the app is quite buggy (you can post blank comments, buttons are sometimes unresponsive, etc.) but for a 1.XX version, it's not terrible.
If you really want to share photos of your furry friends somewhere other than Facebook or Twitter, I'd still recommend Peterest as your first stop -- it simply has a better layout and more-polished features -- though Petigram may also be worth checking up on down the road.