As someone who has paid for commissions as illustrations for my chapters, I can throw in my two cents. It's good to be clear about what the customer will get for your prices. How much of the body will you include at various price levels? Will this be simply line art or colored? How much for simple coloring vs. more complex shading? How much does the background cost? How much for an extra character? Since I want complex scenes for my chapter illustrations, these things are important to me when selecting artists. It helps to put all of these things in a single image for quick reference and calculation on the part of the buyer.
DeviantArt is one of the best places to advertise. Try joining a group for promoting your services like this one:
I have a little checklist that I use once I have decided to commission an artist. You might find it helpful as well!
Character Reference Images:
Time of Day:
It seems I can only post thumbnails of the work I have commissioned in the novel format here:
However, you can find full illustrations on Scribble Hub. I'm collecting one-star ratings, so if you'd like to drop me one, I'd really appreciate it! Giving lots of hearts is appreciated too, but for stars, just one star and no more, please