Ever hired an artist?
_delirium: Most of the artists I know who do small-to-medium contract jobs browse the "gigs" section on Craigslist for their local area (you'd think location wouldn't matter, but a lot of people who contract out for art assets want to meet in person, so many artists don't bother searching outside their local area). It's mainly big in the U.S., so may not work well in other countries. If you're near a major U.S. city, though, a post with an outline of your requirements will almost certainly get multiple responses with portfolios/bids/etc.