And often those were done by the last great true "pulp" cover artist(who's still alive and even on Facebook), Earl Norem. Another of his:
What I remember, and perhaps this is a codependent love of mine since the point of such covers is, after all to trick you into buying it, is that covers like this all by themselves almost outdid whatever could be inside. I like this picture far, far better than I ever could the movie.