Everyone has an opinion when it comes to book covers.

Like divorce and roulette, people aren't shy about giving you their opinions about what works best, what the public want, and what will sell the most books.

I only have one piece of advice - do what you want! Not what someone else wants.

I design all my own book covers because I enjoy it and I am a bit of a control freak when it comes to artwork. I like some better than others, and that's OK. At the end of the day I get to tell myself that it really is all my own work and not a hodge-podge of other people's ideas. As for sales, who knows? These days it tends to be a numbers game based on the volume of your social media followers. Maybe that's why I have so few sales? :) 

At the end of the day, try and enjoy the process. If you get frustrated (and we all do) walk away and come back later. Sometimes changing your physiology changes your psychology.