I still sell on etsy (they screw with you all the time), and am trying redbubble. The problem with society6 is that IF you put your images on any clothing it goes on kids clothes too -- there is no opt-out. I don't think some of my images are appropriate for kids -- not porn, but just not appropriate. I tired zibbet but got no sales in a year. ;( ah well. Now I am selling on my own site: http://www.dkatiepowellart.com/index.html
Hello! I'm very happy since I'm on Redbubble because I can see there is activity and every week I have a sale or two, maybe it's only a sticker sometimes but I don't mind, I'm not here for the money but for the fun and for the experience. I like studying how people react to my designs, how many visitors each different artwork receive, which of them get purchased and so on.
In the past, I also sold some items on Etsy but there were two things I didn't like: you must get rid of your originals (or get them quality printed on your own) and going to the post office is a bore.
I recently uploaded 3 or 4 things of Society 6 but I find it is a lot of trouble to get your images in all the different sizes they require and as I am happy on Redbubble I decided to give up. We must have time for painting and drawing!
I don't know Zatista, Zazzle and Cafepress but I think I'm going to have a look at them now.
I hope this may help you in taking a decision. Good luck! :)