Technically no, you'd need to also deploy a NFT smart contract that creates a new token for each file. But theoretically any media type could be represented by an NFT so it's sort of an arbitrary restriction by NFT.storage. Probably not super enforceable on their part. I imagine the promo will end at some point though. Filecoin just happens to have an excess of available storage right now, which is why they can afford to offer it for free.