I like the originality of the design. I have honestly never seen anything quite like that armor and weaponry before. The giant slab panels on their sides are probably the reason for that, and the idea of a gun being nothing more than a bet-fed cylinder (a HUGE cylinder) is just plain sweet.
However, it's difficult to discern what is their head and what's a shoulder. Though... one could argue that that's a brilliant design choice to ward off snipers aiming for visors. Fridge brilliance, there.
I must compliment the decals on the armor and equipment. The red spade on the gun adds to the mercenary feel, and the rank chevrons establish a firm military 'precision and order' feel, and those red spikes (missile pods? bazinga) bring just enough barbaric ferocity to balance it all out.
A few criticisms, though... first, the shell casings are epic. But they get lost against that guy in the background. It might have been better to have had the fallen guy in the foreground, bottom left corner, but that would really take away from the 'offensive' feel, and make it seem more like the big guys are making a defensive last stand or something. At the very least, things need to be arranged a bit better next time so the fallen guy remains, but the shell casings aren't lost in the plethora of detail on that side of the piece.
I'm also a little uncertain about the two types of ice represented here. The stuff on the left looks like stationary stuff that's been there for a long time, undisturbed, while the stuff on the right seems to be the same thing, but much more wind swept and vicious. Like the bakground is visibly split in two.... But overall, not too bad, because it makes the background more interesting and visceral.
Kind of hard to find anything bad about this. The details are awesome, the piece is badass, everything about it kicks ass in some form or another, and the colors are AWESOME. Just AWESOME.