My latest terrain idea to populate my Games Table with nice looking terrain and scenery is this Rocky Outcrop. Made from expanded polystyrene foam, a little mortar debris (the spiky rock) and mounted on some 3mm Hardboard (Fibreboard).
The expanded foam needs sealing with a PVA/water mix undercoat or paint before spraying with any aerosols as the propellant in the cans often melts the expanded foam - I hand painted the rocks before spray sealing some GW model sand around the hardboard base. Then I continued with the painting once sealed.
I used my normal recipe of Calthan Brown, with Kommando Khaki and Bleached Bone dry brush highlights. Finished off with a touch of flock to add some interest.
I hope this has given you an idea of how to make quick and effective, easy, good looking terrain! For more terrain ideas please see the labelled posts "Terrain".