Looks a very promising start

Regarding the waterfall, it depends on what sort of overall effect that you're wanting. If it's like the one in film then there are a few products on the market (I'll get the links later for you) that would do the trick but they do need practice before implementing on the final peice.
If you are after something more simple then you could use a sheet of acetate, sand it roughly in the direction of the water and then use a clear contact adhesive such as UHU for the foam at the bottom. We have used this technique at work although it's a bit more refined than might be wanted for a wargaming peice.
Also, for the other terrain, try and mix up the colours and greenery that you will use on them. It will help to make it look a bit more natural rather than the normal brown earth, green grass. I've got a couple of different baggies of mixed greenery/brownery that work well.
cheers
James