I'm also in unison with Willfauld, in that the character doesn't differentiate from the background to well, other than different hue range. I know it's night time, but it is a game, so I'd try popping the character's contrast, and showing a bit more of where the black intersects in through the green armor. Also, in the game, it seems like the suit Master Chief wears is made something similar to metal, so giver 'er some shine, eh.
The background also doesn't seem to Halo-ish to me. Halo games like to use beautiful skies in their backgrounds, where this is a dim purple. Also, the rubble in the background has some red glow on them, but I'm not sure from where. Kinda' remind me of those snes contra games, rather than post future world setting, that Halo is set in. Well, they're both kinda' futuristic, but Contra is more steampunk, or mad max type setting, and Halo's environment revolves around cleaner buildings, with more cleaner type alien culture( if that makes sense...). Damn it, I can't explain it, it just doesn't fit with the Halo type environment, is the easiest I can put it. It's not bad, a little more work will do the trick, just a little ways to get there....