IPFS would be another potential solution. What drew us to Bittorrent for this use case is the (at least original) ethos of clients both downloading and uploadin

IPFS would be another potential solution. What drew us to Bittorrent for this use case is the (at least original) ethos of clients both downloading and uploading cooperatively such that as long as there's any community that values the image, it will continue to be available (which would basically be true for an IPFS implementation as well). But the registry implementation in the "distribution" project takes storage drivers, so an IPFS storage driver is certainly a possibility. In part for me going with Bittorrent was also just an excuse to get more familiar with the technical details of Bittorrent.