I appreciate that your are intentionally looking for realism, but one of the places where these things excel is getting weird. make a "realistic" bugbear or yuan-ti and you will be amazed.
A player in the campaign I'm currently running paid for AI art for a month. She's created a couple dozen portraits of NPC's which I couldn't otherwise easily create: a witch with blue skin, green hair, and chromatic roses all over; a half-elf/half-orc; a giff watermelon merchant; etc.
It's honestly quite helpful: I have created many NPC's.
I have to admit that I was going for something like that - but then loosely based on the Burt Reynolds incarnation coz I'm not old enough to know about the 70s version.