Undoubtedly you can search out many useful photo apps with various photo effects. But if you want constantly updated effects, the following photo app Pixlr-o-matic PLUS should be more suitable for you.
Pixlr-o-matic PLUS is an easy-to-use photo app developed by Autodesk, and designed for both iPhone and iPad. The universal app features simple and intuitive user interface and all kinds of photo effects divided into three categories including Effect, Overlay and Border. Most importantly, Autodesk is still constantly add new effect packs for your creative inspiration, and the randomizer allows you to get a random effect for per tapping. Apart from that, you can also conveniently share your photos with friends via Facebook, imm.io, Dropbox, iTunes, Flickr or Email.
Pixlr-o-matic PLUS with a size of 13.3 MB is compatible with iPhone, iPod touch and iPad running iOS 4.0 or later. The universal app is free for a limited time. If you’re interested, jump to App Store for more details.