Under the "See this deck on other sites" section, could you add a link for CardScans (https://cardscans.piwigo.com)? This site already exists to house images of fronts and backs of every card in a deck, would be easier than people uploading them here. (Additionally, CardScans has already set it up so that each picture is watermarked for legal reasons to protect everyone, which is a feature you may want to add if not already implemented here.)

Alternatively, perhaps adding a way to automatically pull each card image from their site into the page you've already setup (may need to talk to CardScan's creator though as it looks like you can't download the images currently.)