I sell my designs as shirts, stickers, etc on Redbubble, and have had a lot of success there, relatively speaking, since 2012.
I am thinking of also joining other similar sites, like Teepublic, Teespring, Society6, or any others out there. Has anyone used these? I'm not sure, without having uploaded anything to those sites yet, how they compare to Redbubble. Is the uploading process as simple as Redbubble? Do they allow fanart? Do you get a good percentage of the sale? Can you upload your designs to a variety of products like phone cases and bags?
The only other one I've tried before is Zazzle, and all but maybe 2 of my pieces got flagged for having to do with anything even remotely fandom-related (literally even something with a quote by Franz Kafka was flagged as fanart). Also the percentage on there was really minimal, because each of my sales earned 5 cents or so, and they don't pay you until you meet some kind of threshold, like $35 or something. Redbubble pays me at least 20 cents for even the smallest sticker I've sold, and 5 bucks per t-shirt at the very least, and more for other products.