What should I put on the cover of my novel?

I’m having trouble with coming up for a cover design. I want something simple nothing too elaborate. The story is about love but not a romance. Its got murder and lies and magick. There arent really any symbols or symbolic items throughout that could be used other than a mask or the moon. The setting is on an island and then eventual to an urban city. I’m feeling really lost. Especially since I want something original and eye catching. The story is titled “Exist” and I will have the quote “The course of true love never did run smooth.” -William Shakespeare across the bottom of the front cover. I would appreciate any help that you all could give me.