I need a book cover to be designed. The book is a self-publish novella for targeted for young adults and the story is heavy in myth (Greek, Romans, Norse, etc.). I have an image done by my friend that needs fixing and improvements to suit the way I want the book cover to look like. I can send you the image and the description.

I would really like the book cover to look similar to Percy Jackson series by Rick Riordan or epic fantasies novels where the protagonists and antagonists are featured heavily along with settings of their battle. Basically what I require is fixing up and bettering the illustration made by my friend.
Ares with spear on one hand and a shield on another. Mars with spatha and gladius on each hand....