What do people think of Teespring?
This site has been the bane of indie artists and fan parody artists for years. They don't show sellers' info on the campaigns, so taking legal action is complicated. They are slow to remove stolen items and never ban the thieves from using their service or block ISPs which are known to be used for recurrent intellectual property theft. The only ones who get tough crack-downs are those who are stealing trademarks and copyrighted materials which belong to big corporations.
I have an account on their site purely to have faster access to communications in order to have my stolen images removed. It's better to get yourself a real shop on Threadless, Zazzle and other such sites rather than use the "campaign" style ones. They aren't seen as crowdfunding sites. They are seen as havens for thieves to anonymously sell in.