Me personally, I commissioned my novel cover from a good friend who is an artist. I've got a new story scheduled to come out soon-ish, and I commissioned the art for that one from an incredible artist I found on deviantart. It's not finished yet, but it was $30 USD, not too bad when it comes to art sales.
If that's out of your pocketbook range, you can always find images free to use (royalty and commercial use free, methinks) and use canva.com to add some pretty, fancy text on top
That's what I did before I got in touch with artists.
There's always threads here on the forums where people offer to draw your character for free to get practice, as well. You could always hit them up, or make your own post asking if anyone would be interested in some pro bono work!
Good luck to you!