Vulpes,
nefnef,
CeilingFan,
Mirasol and
moredhel Thank you so much! I'm glad you liked it. They don't quite resemble the sources yet :x, but that they do look like people in first place and in the shading style I was aiming for already makes me happy.
Woah, those drawings look amazing! And, similar to Mirasol, I unfortunately don't have any such links/resources to share. 
There are a few subreddits on Reddit where users can share and post personal historical photos, such as r/TheWayWeWere and r/OldSchoolCool. However, the time periods, subjects, and quality of the photos vary widely, so I'm not sure if it'll be of much use to you... (Though, on r/TheWayWeWere, you can filter by flair to get images from specific time periods.)
In any case, welcome to the forum!
Whaa, thank you, that's a great help! Both have good photos, though I loved the r/TheWayWeWere in special due its many "Hey guys look at this neat photo of my grandparent!" portraits. They're feel so natural when compared to the photojournalistic/ads photos of the time, even when they're posed studio portraits. This is exactly the sort of thing I'm looking for!
These drawings are great. There are two obvious good reasons, 1. it helps painting faces. 2. painting a skull from time to time is fun.
You're onto it. Under every face there's a skull—I mean under every one of these sketched faces.
One of the major issues I had when drawing people was mislaying features. People always recommend Loomis or Bridgman for the structure of the head but I was never able to place features correctly over their dry line landmarks. Heads wound up two times bigger than intended, features swam on the face and slid sideways. By the time I reached the ears the rest was hopelessly misshapen. I was sure this happened because I was lazy and undisciplined and clearly wasn't trying hard enough to plan my drawings. Turns out I might have some aphantasia going on. Aphantasia is the inability to visualize things in your mind.
I realized a big chunk of the population can actually see things in their minds a couple of years ago, yet only now I grasped how it affects the way I (didn't) draw. Sometimes I'd get asked things like "How do you transpose the character you imagined to the artwork?" and internally I'd go "?!?! What do you mean? There's nothing in my head". I barely sketch before painting, I just throw odd lines, blobs of color and feel my way; I've always described my struggle with lineart as "I can't see volume in the lines". In hindsight even the language I used hinted at the issue: I have a hard time visualizing where I should place the lines, haha!
This is where the skulls come in. The main features I need from them—eye sockets, temples, cheekbones, etc—are strongly tied to each other and quick to sketch. You only need to measure one thing, you don't need to plan in advance nor project anything. They also give something solid for me to grip on as I sketch ahead. The more familiar I get with them easier it is to feel where the features laid on top of these organic landmarks should go. This is not the only thing that clicked last week, it was really a conjunction of things, but it's a main one.
Songbird your sketches are the just the awesomest 
I'd love to see more art from you. And I'm glad you're having fun sketching! We have it in reverse, I'm trying to learn digital currently. I remember this one account that you may like but I just can't find it right now. But I'll let you know if I do.
Hah, two artists crossing paths in opposite directions is oddly appropriate for some reason. Ah, and I think I saw your painting in the other thread, with nice brushwork and a lovely blue palette. You're not trying, you
are learning. I'm no specialist of course, it's just that I've been there and I've seen other artists there and I see increasing confidence in those long brushstrokes you laid on the ground. Good job!
About more art... hmmmmgh... Professionally I moved to a parallel area and I've been taking an extended break from painting since then, even personal pieces, because it kills my hands now and worse, but... *shifty eyes, whispering* My avatar. I don't know what I'll do in the future, I might take up painting personal pieces in a more relaxed pace and eventually start to put art online again, but for now have this old TTRPG character of mine glaring disapprovingly at you. :x
