its looking awesome, im loving the lighting, and you should definately draw the moon yourself, i did a quick paintover of what i'd do next, you should use the zombies as a tool for composition, make them more dull too, more gray so we can focus on the character more, also the light from the moon should be lighter, so it defines the shape of the knight that bit better, to make it crisp and eye catching, atm you're relying on just the shape of the night and the light to make him stand out, everything in the whole picture can be engineered to make it more visually striking.
i hope that helps, do some more random rough zombies, add more ranks, they dont have to be detailed, just a few spots of light to define some small forms, and the shadows will work the rest.
Very nice work, very dynamic, i love it