Wow, I love this! you have really captured the game and put some furrys in it at the same time! You seem to have really done the blood splatter very well. Also how you only did the lines on the characters themselves looks good, draws your attention to the characters, then as you look at the picture you notice the small things you would normally find in the game, like the ammo, molotolves, (sp?) and of course the safe room door, with your typical common infected taking a peek in.
only think I can see to improve on is some of the smaller details of your background. Other than that, I think you've done a spectacular job!