Here's how I imagine the discussion for this cover going....
Editor: Ok, we need a new Red Sonja cover, what ideas do we have people?
Artist: Umm, how about Red Sonja just showing us her ass while holding a sword?
Editor: GREAT CEASAR'S GHOST! That's BRILLIANT! How about she's surrounded by some evil vikings too?
Artist: How about instead, we put the moon behind her. But we make sure the light from it doesn't affect her what so ever?
Editor: Well, I guess. As long as we see her ass really well.
Artist: I'm on it chief.