This is an excellent idea. I've tried to make little scenes or vignettes (such as a broken down wagon with guys trying to repair it) to use as terrain pieces (or scenario objectives), and I'm always looking for new ideas.
The thing that kept me from doing more such 'Terrain Dioramas' (I like that notion) is that it can be hard to get the right balance between specificity - that is, telling one story - and versatility, namely making the piece fit all kinds of games and scenarios. It seems to me that this is easier for 'big battle' games - there's always a place for an encampment, or for a prisoner exchange, or a couple of deserters slunking away or whatever. With skirmish games, the terrain tends to be more specific and 'general' scenes won't fit in, as they have much more meaning in the gameplay. And I mainly play skirmish games...
I'm not sure if I make myself clear, but then it doesn't feel as if my thoughts on the matter are very clear

Anyway, I'd really be interesting in collecting and exchanging ideas and making such 'Terrain Dioramas' myself!
P.S.: Perhaps I'm thinking to much in terms of figure vignettes and too little in terms of terrain...