to add to the spaceship idea ...
maybe not only the ship itself, but also a possibility to "connect" it with the other (sci-fi, cyber, alien) sets
something like a starting / landing ramp, a small space-catapult (for the smaller ships) or some dock - tiles [like a big door with some mechanicle constructions to hold the ship in place] , a bit of floating rubble (for the destroyed parts of it) and some repair drones :P