Metal wall with the word Wasser on it. Can blow away, leaves water. Green barrels blow up one square red blow up nine. Walking over it activates stuff. Damages all who walk over it.
Metal shards from blown up tanks.
Rockets you can blow up. Add iron key. Now they have purple uniforms, if we have palette room. Demon dogs - Add red eyes, make 'em twice as fast, twice as much damage, twice as many hit points. Redden their faces, red uniforms with dark flak vests.