Do you sanitise the images that people submit to this website as pictures? I was just uploading a new avatar pic and realised.
If there isn't any kind of sanitisation then you need to be careful, especially if you start getting popular. A well known family IOS game had an easy access website (easier than this though) and certain people put not very nice pictures on the forum so they had some huge problems.
Maybe you have got something there but I really don't want to test it out if you know what I mean!
Thought I would mention it because I don't want to see your website get messed over like theirs was.... it was a website for TeamLava and I don't play any of their games any more.
Make sure you get some one to PENTEST your website before it hits the masses :)