My local game store needed some new terrain. Having already supplied some building ruins and not wanting to just make basic hills I decided to do a badlands/desert theme. I cut rock spires out of two inch blue foam insulation with my hotwire cutter and hot glued them to one inch foam bases. I purchased a Floracraft Molecule kit, one of those school project kits that lets you connect foam balls together to learn chemistry, and hot glued the balls randomly over more one inch foam bases. These formed the basis of alien cactus. After painting I shoved toothpicks into the balls. The large hill/cliff was given a coat of white glue and sand to add texture.
The rock was given a base coat of brown acrylic craft paint which was then highlighted with a drybrush of lighter brown. The cactus were painted various shades of green. The toothpicks were spraypainted red which proved tedious but not as bad as hand painting them.
Since this was to be game store terrain I designed it to cover about 25% of a 6x4 foot game table. I found a storage container with the same area as 25% and "filled" it with the pieces as I made them. This makes use and storage simple, no arguments about the amount of terrain and less chance of damage to it while not in use.