They should be an old species that has come from a very harsh world, something that had to evolve into what it is as we know it, just to survive its own planet.
Or at the very, very least, if I they had to created then it should be by the space jockeys.
Hiveworlds are interesting to explore because they are basically worlds that got overrun and maybe each hiveworld would have their own variations due to the hosts that inhabited the world. So no hiveworld would contain the same Alien types due to host factors.