Per our Terms and Conditions, you aren't able to sell challenge-winning artwork or designs outside of Minted, even if the artwork has been repurposed into a format that we don’t offer on Minted. The reason that Minted maintains exclusive rights on all winning pieces (via a license in art and ownership in other categories) is that Minted awards cash prizes upfront, with no guarantee that the piece will sell. This means that Minted takes great financial risk, but it allows us to bring artists into the marketplace who could not otherwise do so on their own. We invest in the prize money and in the time required to publish a piece to the site, so in return, we must ensure that the product is available exclusively on Minted.
However, the use of design elements (as opposed to the whole design) on other products can be a bit complex. Part of what makes Minted so special is that we only offer original designs that are unavailable elsewhere, so we wouldn't be able to offer a design that was, for instance, printed in its entirety and sold elsewhere on a t-shirt.
With that said, we want to be as flexible as possible and don't mind artists reusing some design elements from their Minted pieces. We need to make these decisions on a case-by-case basis, depending partly on how much of the original design is incorporated in the product. So if you're wondering about reusing parts of your design elsewhere, please email us at firstname.lastname@example.org! We'll be happy to help.