I will start of this thread by voicing my opinions, please follow my lead.
In my opinion a GERMAN veteran should have the following:
1) No insignia on helmet, new fresh soldiers would have yet to realise the potential to snipers of a shiny decal.
2) Rolled up sleeves, open collar.
3) Medals i.e Battle of Poland, France & possibly bravery & Infantry combat medals.
4) Arm decals i.e for Tank busting
5.) Should carry a sidearm, be it German or other.
6.) Plenty of grenades.
7.) Camoflage cover / Wire netting on helmet
8.) No strap on helmet to stop neck from breaking if high calibre bullet hits helmet.
9.) Worn out uniform colouring, possibly trousers old '1939' pattern to show how long he has been in combat.
10.) Scratches / scars on face (Battle hardened)
11.) Dried on blood stain on uniform.
12.) Irregular equiptment i.e more streamlined for practicality / possibility of not gas mask tin / breadbag
13. Nicer officer jackboots which he may have aquired from an earlier campaign.
14.) Leather gloves for winter settings, instead of the standard issued cotton variants.
15.) BEARD!!!!!!!
Some of those are good ideas, although I disagree with some.
1+3, they seem to cancel each other out, also, how would a battle-worn veteran (that has a beard) be able to have medals on his jacket while jumping to cover etc, a guy with torn clothes but some shining medals? It's a battlefield, not a parade.
2: Might get might cold in the winter, boy.
6: Would that be a change in gameplay, or would they just be visual? Either way, I'm not sure what to think about it.
8: A helmet without a strap doesn't hold on to your head pretty well without holding it with a hand, unless of course the helmet is so tight to your head that it doesn't move at all while running, and if that gets hit by a bullet, it won't protect you that well.
15: Not everybody likes beards, wouldn't imagine that every veteran had those in every single battle...
Edit: Apparently most of these things were already said, so I'll say one more thing; the angry machine gunner from the mini series Shtrafbat is actually an orthodox priest, that's why he has such a beard. Also, about having old clothes, the men did get to wash / change their clothes sometimes, supply lines weren't only for food and ammo.