https://assetstore.unity.com/packages/3d/props/sci-fi-hsk-props-56497 This asset kit has some interesting stuff. A generator looking model, a bunch of computer consoles, some containers, some machinery type deco! Those two pieces in the top middle. I'd love more deco like that. Computer consoles too. Maybe not something they'd want to buy but it might give the developers a few ideas.
I found something interesting that I hope the Devs like. I know that they have been working on their own world-generation engine for years, but you cannot beat the price and it may be able to give them a new perspective that they can use.
https://assetstore.unity.com/packages/3d/characters/animals/fish/seaanimalspackv3-90353 I can't be the only one tired of lifeless seas, can I?
For planets and stars and maybe other effects : https://assetstore.unity.com/packages/tools/level-design/space-graphics-toolkit-4160 For place objets on planet and water translation on planet : https://assetstore.unity.com/packages/3d/environments/sci-fi/cosmoscape-space-environment-art-129370
A little expensive, but it's on sale. SCI FI CHARACTERS MEGA PACK VOL 2 https://assetstore.unity.com/packages/3d/characters/sci-fi-characters-mega-pack-vol-2-186888