Well, the Moloch is very finished, it's Nyx's most recent shivan contribution to the FSU and at least to me, it is gorgeous. The revised Rakshasa I also consider done, unless someone points out a significant way to improve it.
But, what's creating the effect you're talking about is that the ships are, in essence, catching the light from the nebula in the level background. Their ships are practically black, but they are not coming 'out of the shadows' in most of these shots. They catch the light, and they have to do that at least some or they look very flat and dull, IMO. To see the backgrounds reflecting off the hulls of the Ravana, Demon, or Moloch, or to see how their own beams light them up, or just how their contours catch the light of a level's sun(s) makes that flatness of the other ships painfully evident to me, and thus this effort.
The current MVP version of the Rakshasa is first image, and my revision is second. I would point out the upper curve, from midsection to back, of the Rakshasa. I would say my version is overall quite a bit darker, actually, closer to being a black metal than a grey surface, while the underside is lit a bit more but in the colored lights of the background nebula, not in the white light of the sun.