If you're any what familiar with how id created the monsters and art for DOOM you'll know that they were actually referenced from clay models that they made or used objects like toy shotguns.

One of the things thats puzzled me the most is the identity of https://7chan.org/vg/src/134469687392.gif. Who is he? Stock photography? A developer?

I'd love to know!

Something tell's me he's just a generic face they made. Not every sprite was made from real-world objects, and I think this is one of those things they just made by hand.

It would make sense, too, there's no need to make a model for it if it only faces forward. This makes it easier to have a "base" face that you can draw different expressions on.

I could be wrong, but I don't see why they'd take a photo for a sprite that faces only forward.