Farewell, My Lovely is a classic hardboiled noir book from 1940. There is one scene in it where a character gets hit upside the head with a bedspring . . . but is that really what you want to put on the book's cover?
As to romance books, they have their own cover formula of steamy girl/hunky guy.
So what went wrong here with Craig Douglas's 1966 romance The Hungry Ones? (Via.)