Book covers have a lot with the size of the publisher you are dealing with. Don't expect a small publisher or a self publisher to have the financial resources to give you a Boris painting or a Rowena painting cover for your novel. They are high priced fantasy cover artists. I happen to know twenty years ago Boris was getting paid one million dollars per cover.

Smaller publishers cannot afford the services of high profile cover illustrators.

They have to use the services of overseas graphic design companies. They can be hit and miss with their work.