Illustrators and authors work together to create an environment that moves plot forward. Coloring and tracing can inspire calm, urgency or peril.
I can say that half the time the story was inspired by images. I had the monster, but the details of the worlds and the cityscpaes. Those are best done by an illustrator that can capture your mood.
Illustrations by Bob Eggleton (9-13-1960) who’s extensive work appears on the cover of many Science Fiction magazines. He is the recipient of: Hugo Award 2001; Chesley Award 1999.