I used to have two coworkers who wrote romance novels. One day at lunch they were telling us about the cover art. Apparently in the romance genre there's a whole coded subtext there. What the characters wear, how ripped the bodices are, who is touching who and how, it's all a precise code that conveys exactly how steamy the book is, and what kind of steamy.
How much of this exists in SF?
(One of my coworkers was black, and wrote romance novels for a black audience. She was considered fairly groundbreaking. I wonder if there were any differences in how this code applied to her cover art? I don't recall her saying anything about it.)