I would like to see a figure on the cover, but her face shouldn't be the focal point. Using magic, or in combat with another individual (there are several duels that take place in the novel) would be nice. The main character is a 14 year old girl, tall and incredibly stubborn. She fights with a sword and her magic, channeling energy through her hands. The Emperor god is immortal, with the appearance of middle age.
There are two major duels in the book. One is between the main character and an older woman. Both are Kinetics, so they can channel energy. In that duel Erin (the main character) has a sword but the older woman is unarmed. The duel takes place in a dilapidated basement, lit only by sunlight coming in from cracks and holes in the floor.
The second major duel takes place between Erin and a middle aged man. The man is a Shadow, an assassin that specializes in killing magicians. The Shadow does not have any magic, but he uses poisons and subterfuge to win. Erin is unarmed in that fight, but the Shadow has knifes and a poison filled needle (think of the assassins creed hidden blade but instead of a blade it's a needle filled with poison).