Bren--Glad you like the idea. Here's a top down picture of a North African dio I made with fairly rocky terrain.

I used Celluclay (papier mache) to get the shape of the ground and, while it was wet, I placed in various sized model railroad talus (you can use larger pieces of sand or small pebbles for this too). Fine sand was sprinkled lightly over top to get the right texture and everything was stuck down with a coating of thinned white glue sprayed through a bottle. After this, I just painted it the colour I wanted, using a couple different shades, then washed and drybrushed as I would on armour and finally added some ground pastel chalk here and there. If you want to read more about it, I wrote an article
hereHope that helps,
Nic