I have posted art work on these sites so far:
Artbyus.com - posted image for a friend, however, no response and if you page through the images does not look like there are any sales.
Leasebyart.org - posted images on this website, however, no response. If you page through the images does not look like there are any sales.
Redbubble.com - somewhat like Imagekind offers both prints and t shirts
It appear that most of these websites appeal to artist and artist are looking at other artists work, but the general public is not being attracted to these sites and no sales.