Well, I said I would do it, and I have. Here are some photos (badly taken) of my diorama of the Battle of Waterloo.
It's size is about 3.5 feet by 3.5 feet. It is very small but that is because I have to keep it in my bedroom, so I don't have a lot of space. I have a wooden panelled base, with layers of sculpted construction foam on top, with a layer of plaster for final landscaping. As with most of you, I painted the whole thing earth brown, and then added the grass, bushes and trees after.
I hope to one day have enough room to build a big diorama, where I can add lots of figs, but I will be leaving for university soon, so i'm afraid that day is a long way off.
In the mean time, here are the pics.