A couple of observations:
First, the ranges are going to be something that hasn't been done in a toy soldier before. This was discussed back in March around the time of the West Coaster. So, that leaves out anything mentioned in this thread. Andy won't say what they are except what they are not: no Flashman, no Franco Prussian War, for example.
Second, and further to Harry's posts, the Northwest Frontier and India, in general, is a fascinating period of history, probably one of the most interesting. I have always been intrigued by India ever since I was a kid and would love to get there. In the toy soldier world, this has been visited and the results are wonderful: Somerset's ranges, Delhi Durbar, Camel Corps, Britain's Sepoy Mutiny (wish I had the room for that). In my view, and only my view, a lot of more interesting than cowboys, etc.
In addition to the suggested reading, you might find Queen Victoria's Little Wars an interesting read. A brief survey of some wars from the 19th century. Author is Bryan Farwell.