How light affects a face http://www.zvork.fr/vls/
Skull rotation (any species&human) https://x6ud.github.io/
Hair catalog https://www.hairfinder.com/
The Hairstyler https://www.thehairstyler.com/
Period/Fantasy costumes https://www.osfcostumerentals.org/OSF-Costume-Rentals
HD royalty free images https://gratisography.com/
Character Design References https://characterdesignreferences.com/visual-library
Figure Sculpture Gallery https://philippefaraut.com/collections/figure-sculpture-gallery
Pinterest https://www.pinterest.jp/
SketchDaily https://www.sketchdaily.net/
3D scans of a lot of stuff https://www.myminifactory.com/scantheworld/full-collection
Google Arts & Culture https://artsandculture.google.com/
Web Gallery of Art https://www.wga.hu/index.html
VADS https://vads.ac.uk/digital/
Valve Archive https://valvearchive.com/archive/
Stock Photos https://gfxmountain.com/stock-photos/
FromOldBooks https://www.fromoldbooks.org/
CopyrightFreePhotos https://www.copyrightfreephotos.com/
Generate fake portraits https://this-person-does-not-exist.com/en
Idol/cosplayer references https://idol.sankakucomplex.com/
Same Energy https://same.energy/
Big Box Collection https://bigboxcollection.com/
iTunes Artwork Finder https://bendodson.com/projects/itunes-artwork-finder/
The Poster Database https://theposterdb.com/
New Old Stock https://nos.twnsnd.co/
PhyloPic https://www.phylopic.org/
Danbooru https://safebooru.donmai.us/
https://thefcdproject.tumblr.com/
https://herorps.tumblr.com/fcd
https://peppermintstranger.tumblr.com/directory
https://roryrps.tumblr.com/fcd