In the first image there's either a rococo level of greebling or virtually none. There doesn't seem to be any rationale, even an in-game reason, behind why the ship looks really busy in one part and and nearly bare in another. (Note that I'm not saying this ship looks bad in any absolute sense; we're just comparing relative approaches.)
By contrast, the Star Detroyer's greeble is well-distributed. It sort of makes sense that the flattish surfaces would be mostly greeble-free, and that the areas exposed in between flat surfaces might have high-variation greeble. Even if it's a little weird, there appears to be a logic of some kind that's determining why some parts of this ship are complex and others are plain.
Well, if that's the case -- how do you do that procedurally? What's the algorithm for greeble that's:
- pleasingly "noisy"
- varied between ships, but still similar to other ships from that culture
- highly varied between cultures
- efficient to generate