Maybe you could make a page where people can upload photos and when they are approved they will show up and you can download them to the area where the hopscotch characters are when your editing
I know some people don't like the picture idea but I think it helps when you need a zombie for example
I like your idea where the Hopscotch Team would have to approve pictures. The only problem is that there are thousands of Hopscotchers, so it would take a long time to get a picture approved. It might also be confusing if, say, a picture was blurry or not in focus.