What I have is some art that was drawn specifically for me, no one else owns this and I can convince any potential buyers. What I have is a few character designs that cost around $50 each, various monster designs and various item designs that I never used. I would like to sell them but I don't know where to sell them. Anyone help anyone?
RedBubble.com, Zatista, Ebay, ImageKind. You could also sell on other formats (cups, frisbees, etc) via Zazzle or Cafe Press.
Speak to Opus. They specialize in original pieces of art, sort of like a real gallery. They have an office located in London too:- opus-art.com
If the artist is planning on making a living out of it and committing to uploading new art daily, then dailypainters.com is a fantastic site ... well, I guess it's mainly for painters, but they probably would accept illustrators as well I'm sure ... but I'm not sure about sites for re-selling other people's art unfortunately.
If you want make a little more than 5 bucks, try GigBux, you can sell the art gigs for ten bucks or twenty bucks.