I'm going to tell you something scary, I was thinking about making a Zombie Apocalypse story called After The End but I wasn't going to call it the walls just After The End and I was going to use the exact same picture for my cover as well. Now I'm sorry I haven't actually read your story yet but if its a Zombie Apocalypse story I made a Layout that I shared that you can use if you want. I made it for my story originally but I shared it because I haven't seen any layouts personally made for Zombie stories.
Its called Zombie Grey.