WARNING: This post might be graphic for some people, so if you don't like too see it go back now!!You sure about that? his hand is larger than the skull. I know they would be smaller w/o the flesh and carnage, but still.. that seems smaller than normal.. whatever though.
Remember dead body's swallow up after a while. his other hand looks less big.
more odd is the distance between head and body, for a neck it should be too far from his shoulders.
The might did ad a skull later for propaganda reasons, and placed the arm in front of the neck so you don't see it's fake. but moving a limb of a dead person is very hard! it stiffs up so you might need to brake it.
It's not the first picture I have seen with a full visible skull.
for example this one:
I understand in a muddy dirty conditions with rats everywhere a body might rot quicker, but that fast?
Maybe gas helps rotting it faster?
This photo however looks more like a body that is rotting, although in a strange way?
edit: After google-ing:
The corpse of a German soldier killed during the Allies' Somme offensive, face stripped to the bone by rats, lying in a trench near the village of Beaumont Hamel, late 1916.
Rats it is...