Yeah, I would second the previous posters. It's going to be finding some good reference, and searching for the areas where you can put in your darker values that'll help it look less flat.
I did find a reference that might be able to help you out with forms if you're going to keep the front lighting for the final. reference1
For a more side lighting solution like Malcolm suggested, this one might help a bit. reference2 or this one. reference3
Adding some extra details in the hair, ears, and neck area in the addition to the face might help as well, though I would still keep the contrast lower than the face, as to not become the main attraction for the eye.
Some sketches to help understand neck anatomy a bit:
As far as a vampire look, you could maybe look into Selene from the Underworld movies. She might make good reference for that.
I think it's a mixture of the glowing/unnatural eyes, fangs, and fairly colorless (from a lack of blood) skin. Malcom did a nice job with keeping the colors you had, but pushing the more red hues into the shadows, making them seem like part of the lighting, and reserving more desaturated/dead colors for the base color of the skin.
You can see the same effect in the Underworld's color correction reference4
Best of luck with the contest.