Does anybody have a good software recommendation for converting normal photos into zombie pictures? I'm looking for a variety of different images to round out my "cast" of zombies.

The Walking Dead's "Dead Yourself" app springs to mind. I believe it's a free download from the iTunes App Store, not sure about availability for other devices.

Edit: You can create zombie versions of real people in your life (who were zombified in game) to further enhance the "playing as you" angle, or you can take snap shots of random people / load up pictures from your computer to create other zombies with.

How about screen shots from The Walking Dead? The Dead yourself app does work good too IMHO, though you wouldn't know that judging b the horrible examples that they pick on the Talking Dead for their contests. The app really needs to be used in a certain way, facial alignment and correct depth is important otherwise your zombified face comes out looking really out of proportion and just wrong (not wrong in a human sense wrong in the sense of facial form and proportions).