This is truly striking pencil and ink work. It's not what I'd be looking for as any of in-game, game box/manual or game advertising art. That's all that's negative about it though, is that it's not something that's of use in selling a game.
Your understanding of draftsmanship and shading is excellent, and the use of the black ink for deep shadow and red for lips and blood as well as red for the lettering adds impact to the piece. In fact, I'd suggest that this might make a better book cover for a novelisation (if there were one) than a full colour picture would.
Turning to your "Toph Beifong" piece that you've coloured, I can see the same standards of draftsmanship and understanding of light and shade in the colour work. The tones clearly aren't fully realistic, but the picture has a nice colour Anime/Manga feel to it, and would stand on that level if not against the competition semi-finalists as realism.
this should be pretty easy to color in photoshop. I say color cuz the way you did it don´t leave to much room to actual painting. You should give it a go, and experiment on PS or any other software. It looks gorgeous though. Really cool