Faces
I wanted to show some of the facial variety I had in mind for my original characters.
Pre Code Horror Scene Drawing Studies
Three Fourth’s front view is the most difficult for me to ‘invent’, and reference study helped alot. 
This is a study of a still from
‘Theatre of Blood.” A unique dynamic perspective; hitherto, difficult to invent.
Forshortening of the face and torso, was difficult for me to ‘invent’. Many studies, helped make it less difficult. This was from a photo set of asian models.
Gesture and Expression
I like how the slightly exaggerated athletic physique of a track athlete drawn naturalistically appears – over the formulaic standard. I like both, but this adds to my repertoire something that can make certain character illustrations convey an informed, function specific musculature. 
Lip musculature, eye squinting, that I could not invent. Useful for expressive panels, and angle (tilt) of head poses.
Creatures
Catra (Masters of the Universe – He-man, cartoon stills) – I wanted to have a cool looking cat for my characters to ride. Started by studying some. *
* I’ve studied actual big cats from photos of real animals. So I wanted to study some professional cartoon cels, to have the sense of how to present a giant cat going through the motions required for movement, and carrying a rider.
When applied to my own giant cats, I could base the general action on the referenced study (drawn freehand ) but embellish with details from actual big cats, and use my own unique costume/armor design, and proportions, to create something that looks the way I want it, and conveys the action precisely – original and different from the reference.