Here's glimpse of the design process of the main (possibly only) inhabitants of the Reserve, the Screwies in The Book of the Dead teaser. If you want to read more on the thoughts and ideas that went into designing them
check the full blog post here -
https://blogs.unity3d.com/2018/06/01/book-of-the-dead-concept-art/
In a lot of the later stages of design we collaborated closely with Plamen Tamnev make sure to check out his awesome work for insight into what happened on the character art side:
https://www.artstation.com/artwork/Lzg6k
https://www.artstation.com/artwork/5yKlJ
Book of the Dead - Unity Interactive Demo - Realtime Teaser