In theory you could use any terrain element, a tyre stack, oil drums, rocks, crates, a fallen tree, sandbags etc.
These two ammo crates come with the Dust Tactics: Revised Core Set.
Simple enough to paint, undercoat, base-coat, wash and gentle dry-brush. Decals added (leftover from an old WW2 model kit) and then a quick coat of matt varnish.