What is final art in ship development?

I would say, well, final art is basically just a level of polish. At least in my head anyway, it's going through it, validating, that's a good word, isn't it? Going through checking all the shaders, materials, performance in terms of amount of shaders, does everything operate as it should do, animations, VFX, lighting, fog volumes.

Decorating the scene, as it were. If this were a set, this would be the set decoration.

Yeah, adding props and finding opportunities for life, basically, where you want little blinky lights or whatever it is that you want to put in the ship.