I used the app, Poster Maker, to create these posters. While the user interfaces aren't always the easiest, the available fonts and backgrounds really give these publicity posters a professional feel.
I was able to use PosterMaker in conjunction with photographs that I already had on my phone. Fortunately, I had plenty of suitable photos available. I think this one captures the creepiness of urban Atlanta at night and has a bit of a zombie feel.