Honesty, it is hard to beat old-school hard-shell techniques. Define your contours using free crumpled-up newspaper or cardboard strips rather than expensive pink foam. Then drape it with paper towels soaked in thin plaster or some kind of glue mixture. Be sure to add an occasional escarpment using thin pieces of carved foam, broken ceiling tiles, or even real stone. Next, paint the whole thing flat black and then dry-brush lighter highlights. Finally, sprinkle your favorite ground covering--the more variety the better. This technique costs almost nothing, is not heavy, and looks great.
