So my designs have been on Redbubble for just under a year, apparently is supposed to take just over a year before they sell but I appear to have started :) Here are two of the things I've sold so far...
You can find them here if you would like to buy them or have a look at other things I have on there: http://www.redbubble.com/people/sarahjsjackson/works/8967184-geekasaurus-colour?p=t-shirt
But I would say if you have spare textile designs knocking around that you're not doing anything with, put them on there! It is worth it, you don't get much income but it's something and it helps towards your online presence, the more places you have examples of your work the more likely you are to be spotted, so it is definitely worth doing!
P.S I've had another bit of luck as well, someone found a photograph of mine on flickr from the Student Protest in London 2010, and they liked it and its now being published in a book. Using as much online resources as possible is so worth it!