Redbubble is and has been around awhile. My favorite thing about them is that they were one of the main competitors to Cafepress (CafeDEPRESS). As long as you aren't looking for nor wanting to design and sell pop culture designs (DMCA take downs) they still are a valid option. Orignal art and concepts such as the Screwed design with the scuba diver shown below.
Redbubble Is More than Just Tees.
Not only do they sell various styles of graphic tshirts with an industry average print quality (still light years ahead of Cafepress) they have outstanding Sublimation printing on products such as throw pillows. Other products such as: Device Cases, Stickers, Greeting Cards, Wall Art, Home Decor, Stationery, Bags, and more give shopkeepers and customers tons of options to get started. And there is no time better than Halloween to begin the venture.
In conclusion, for anyone looking to get their feet wet by opening an online shop Redbubble is a favorite because of their extensive advertising and open communication such as with their customer service.