Quick and Dirty: Go to Image -> Adjustments -> Levels, and then mess with the three nubs under Input Levels for your dark darks, mids, and whites.
Involved: Or if you know about photography a little, you can go to Filter -> Camera Raw Filter, near the top and mess with all the things, bring that exposure down, eye-dropper white balance it, mess with the whites, shadows, highlights, contrast, etc.
Although the way your backgrounds are blown tfo, I'd recommend opening up your fstop when taking the pictures so that there's information to mess with, as it's probably zebras back there.
Tips from a fellow beastclaw raider painting his first army!
