That's a really good approach as long as the style fits. You can't beat free!

@DonThiebaut Given that my novel is about celestials, it did seem appropriate. And I didn't have to pay a cent for the cover (plus, I now go scouting for stone angels everywhere I go).

It's a humorous story about a young man who moves back to the house of his childhood after his father has died. He finds a robot hidden in the basement. I tried drawing a picture of a robot in a suit and carrying a briefcase walking down a residential street. That was what I wanted but I can't say that someone else might not come up with a better idea.

@RRBinkele That's a good start. Humorous helps, it makes the realism less important. Budget is the next concern: big name pros can charge 1500 or more. The more moderately priced folks are often in the 200-500 range, if they have a stable income and a full portfolio. New artists are best for cost, but are a gamble on quality, reliability, etc. With a less serious tone, I would suggest a newer artist, though not completely unproven. You can go on a site like Deviantart.com and search for the things you like, then bookmark a few artists that have a style you enjoy. Send a few polite messages stating your interests, what you're looking for, and when you get into an arrangement with an artist, remember to let them take the reigns as much as possible, without losing focus on the things that are really important. They'll know better where the shadows should fall, or what proportions look right, etc. You just gotta make sure the vibe is right and let the details work themselves out.

@DonThiebaut Many thanks. I'll check out the website you mentioned.