Google image search for "cthulhu" it turns up a ton of stuff
Searching this will limit your results.... try Lovecraft, as you will get a much wider image serach result...
Also, if you own or know somone who owns or just go to your local gaming shop and pick up a copy of the Chaos Inc's RPG.. just look though it and note the names of the artists who do the drawings.. if you go to their personal web pages you will get VERY high quality art, and tons of it.
Try and get hold of "The Art of Lovecraft: Artists Inspired by Lovecraft."
some really great stuff in there