Just one nitpick: his abdomen looks a bit weird, can't tell if the anatomy is correct or not but I think in this light it should look more hollow, like in the gif last frame with raised arms.

Mr Thompson is awesome =)
Only thing is his dead eye could be more obvious and scary if it was larger, as people with such impairment usually develop facial asymmetry because (my guess) their useless eye muscles relax into oblivion.

the slight view from below

Ok, wasn't sure about that. It's a perspective issue then:



Hope it's clear without more explanation =)
Of course this is based on the assumption that the pose is straight, which seems to be the idea. But his right shoulder would probably be raised by the arm position.
I'll also add that this rather strong perspective means a wide angle view / near p.o.v.: this would tend to decrease, not increase, the apparent size of the lower legs and feet.
I'll try to find a photo example of this, will post if I find one.

Much improved version btw =)

Not bad 

The head looks small, in both anatomy (considering the thickness of the material that covers it) and composition respects.
A much larger beak would help making it the focus.

The piece might be drowning in detail, I'd love a few quieter eye-resting places in shadow, esp. in the areas of repetitive detail such as the ammo belt and fur.

The ammo belt should cast a shadow.

The weapon could use some wear and tear, rusty patches, dents and stains. The shaft has significant banding.

No AA at all?

Edit: funny how peeps see different things.
Night is right about the arm, and actually it's worse than that: the whole shoulder line is horizontal (from our pov) whereas other similar lines at feet, knees, pelvis and elbows levels are not. It could be considered perspective from a shoulder-level pov, but it doesn't look like it (specifically, it would mean a closer pov which should be noticeable in other respects).
This problem might even concern the head and eyes too.

Pixelling fog is fogging difficult, as evidenced by this challenge. Animating fog must be hellish.
Also you don't see fog move a lot at small scales IRL; don't be fooled by movies (they use dry ice).

For what it's worth, my fave fog pixel; Skeddles' fave fog pixel