You need to go after that vendor - It's says over 70 sold. At the very least you get an EL for each different design sold. Good luck, hope you figure out where they got them, that would be a starting point.
Unfortunately with partner programs, many people will never know who sold what, to whom, for how much. Total loss of control and rights.
Go after the vendor, not Groupon, but if there's a legal action, include Groupon for handling them. I suppose the current examples above, the image owner could notify Groupon that the product is being produced illegally! Shut them down.
I have grabbed screenshots of everything and found the vendor that offered these through Groupon.