Digital Dude here. One of my favorite iPhone apps right now is PhotoForge. It has an impressive little painting program that allows your to turn your photos into "masterpieces". Well, come on, it's all relative, right?
You use your finger as a brush or you can get a stylus. I use both. Here are three before and after examples from a recent trip to the Sierra. The first two I painted and then took into the app CinemaFX and added an effect called Color Comic which made it even more painterly. The last one I actually took into Photoshop and used Topaz Labs' Clean to finish off the edges.
Give it a try, but be careful, it's truly addictive!