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
I looked through about 3 pages of these creatures and though tha the creator was just thinking about making something that didn't exist as such out of horror or twisted sciece. But I feel that if you wish to create a realistic sci-fi creature (that's funny in itself) you should start with the environment, it's terrain, the atmosphere, the food available, the dangers and the competitors that it may encounter, how it gets to where it is now, and what might have shaped it's development, For example a low gravity would perhaps favour a taller slender creature, it's muscle tone (weak) would be evolved for that low grav enviroment, perhaps if there was a lot of helium in the atmosphere it might tank this and glide, or perhaps a much shorter wider very strong boned and muscled creature on a high grav world, far less likely to fly or have airborn creatures, what food would there be? how would that food grow if plant based... it takes me right back to Mark W Miller's Traveller.