Apparently in your Submission Policy, you claim you can take whatever you want and use it however you please when it's on your site.
You know, that's kind of a bad idea to have. Especially since you're a hosting site. I recommend you correct this policy, because it's asking for trouble. Especially if you take something from someone and sell it without permission, but they own the legal copyright and/or trademark.
I say this because, if you sell something without the express, written permission, on the conditions of the original owners/artists involved, you're likely to get your butts sued off.
So, two options: Either you change and adjust your policies to protect your creators and offer them a deal when someone else wants to use their work....OR, in the future, you get one or more pissed off individuals that own copyrights/trademarks that you utterly stole out from under them and infringed on their rights, where they effectively, I don't know, sue you? Costing you more than you made? Hm? Does that seem worth it to you?
Because, you know, if you stole my works from me, I would indeed come after you legally. Hell, if anyone stole my work, I'd come after them in a legal sense. So...are you sure you want that policy the way it is?
Unless there's something I'm missing of course.