I get asked all the time where they can buy my stickers or buttons. I don't always have extras or want to buy one just to ship them one, so I think it would be a great idea to offer a way for people to sell the designs they have uploaded on StickerMule. Obviously, then you front the cost for potentially sending one sticker to one dude in Alaska, but this would dramatically increase your sales, I would think.

Spreadshirt would be a good model to copy.