Gday Alec
This is the first I have seen of this, and I'll start by saying that you have taken on a lot!
No doubt there is a lot of effort gone into this mate. What is the plan~ are they to be individual segments around the same theme, or a continual scene only segmented for handling purposes?
Is the scene of the Western front? I believe there wouldn't be the tree lines shown, as the artillery would have reduced the landscape to a barren cratered waste.
I reckon, and especially for a beginner, that you start with one segment and really work on creating a complete storyline within that scene itself. Too often the excitement of creating dioramas leads one to go well beyond the limits of 'controlling the scene'.
I see a huge variety of groundwork combined, and they seem to overpower the scenes and harking back to an earlier observation maybe you could run with limited 'additions' and really work on making the actual ground look realistic, pock marked with shell holes etc. and go for a more simplified approach. Less can be more in these instances!
A+ for effort though
Brad