Agree 100%, congratulations Julien! I meet that kind of guy all the time (albeit without helmet) on my way from work and the expression is exactly that one.

One thing that puzzles me though is the viper tongue on his lower lip?

My first thought when I saw the red spot on his lip, "He looks like he bit someone's ear off!". Obviously I have too much imagination but he does look like he's in the grip of battle fury and trench raids were brutal affairs. It could be a wound from where he's been hit in the face during the fight. I wondered if the red stripes on the skirt of his tunic were blood splashes but I think they're probably facing colours.