I am assuming this diorama would be set in a wooded area in the middle of nowhere and would be a field work, not a permanent installation? If so, here's some fences and a MG tower, taken straight out of a German field works manual. There are many more types of fences, and a shorter version of the tower. (similar, but basically omit the bottom set of legs on the tower.) Major airfields could have chain-link fences with coils on top, but I'll let a fly-boy discuss the details on that, I'm just a tread-head.
If these don't copy well, go to: http://rongeorge.com/modules/Gallery/upload
and find them there. They should zoom to legible size there.