@black_elk It looks to me that those units are about 48 pixels wide. I mean the ones which you uploaded in a single image in this thread.
The image is 4,000 wide simply because of this forum's limits (and because this topic says 4000px). I would go with it being 10,000 on both axis.
This is how it would look with those about 48px units.
7(2).png
As it is traditional in WW1 games, I assume the game would have frequent stalemates, with enemy units sharing the same territory across turns, so I guess it would be normal to have German, French and English units on the same territory for some rounds.
Actually, the original which I made was 6,000 on both axis, but I shrunk it because forum would not allow it.