I think this has been suggested before, but after dealing with a few marketplace items that didn't quite match their description or previews, I feel like allowing a rating system, or at least a comments section, on marketplace items would reduce the need for refunds, as well as giving ways for both criticism, praise, and general discussion on the items to be discussed. In this case, it could also be a way to advise users if something may not be exactly what they expect, as well as allowing marketplace creators to answer questions and receive feedback on their work.