Lou Anders, editorial director for Pyr, Prometheus Books’ sci-fi/fantasy imprint, also serves as art director when it comes to the books’ covers. In an interview with Redstone Science Fiction, Lou Anders, who also, to my delight, rightfully proclaims Ender’s Game to be the Harry Potter of science fiction, had this to say about the process of working with illustrators for book covers:
I… tend to believe that whenever an illustrator shows you a choice of compositions, they always have a favorite, and that if you can figure out which that is and go with it, the work will be that much better. Not that any of these guys aren’t professionals who would execute any of your choices to the best of their ability, but if there is that extra spark of excitement it will make the piece “go to eleven.”
The importance of leadership heirarchy in the design business can never be overstated, but it’s so gratifying and inspiring to hear an editor/art director recognize the importance of encouraging designers to remain excited about their work. In exchange I hope illustrators will recognize the important place art directors/editors have in the design industry.

well-said.