Authors are deliberately excluded from all this, on the grounds that they're so in love with what's inside the book that they don't understand what the cover stuff is for. Which is advertising.

The purpose of cover art is not to show the reader what's inside the book.

It's to get his attention from across the bookstore and get him to pick the book up in the first place.

Half-naked women and muscular barbarians are very good for getting teenaged readers to at least take a look. Black and red are good, too. And spiffy hardware, like spaceships. Cut-out covers,