Part of the reason it took so long for me to complete this is because I spent a lot of time experimenting, since I'm still apparently quite unlearned in 3D modeling techniques, and I got carried away with it, because I kept trying to find a better way to do various things.
The result of my efforts is a model that uses a 16x16 texture and makes use of UV vertex skewing to achieve non-pixelated angled lines, essentially making vector-based angles, which have various benefits, making the model more clean, readable, and consistent from various angles and distances. It's essentially a combination of vector and pixel art.
One of the things that got me thinking differently about UV mapping was this GDC video, in which they show how they achieved clean, non-pixelated hand-drawn style lines with their UV mapping method:
So here's Cthildha's face with the HYBRID PIXEL ART vs STANDARD PIXEL ART:
Personal preference could say yea or nay to the vector-like style, but the reason to choose this style isn't only personal preference. There are some situations where the style would be objectively better than pure pixel art, so I think it's worth sharing. But, while I think the method is good, I did try to push things to an extreme with this model, because I was sort of testing how far it could go, so you could say this is a bad example of a good method, haha.
Here's what I mean by "bad example" - the TEXTURE MAP UVs:
As you can see, it's a MESS. Things are actually grouped fairly logically, but since the original poly shape is lost on most things and everything is also very broken up, it's not immediately apparent what UVs belong to what polys.
I could have made the texture 32x32 and made everything far more readable, but I wanted to push for 16x16 to test certain limits of the method. Of course, even if I went 32x32, there is no getting around the fact that some readability is sacrificed due to UV skewing having to take place at some level.
So UV texture readability is one downside. The other major downside is the poly increase:
That's a lot of polys compared to the standard pure pixel style, which is literally just three planes for the face.
But if you were to achieve this vector style face with a texture, the texture would have to be far larger to give clean enough angles, and it simply could not be zoomed in on without angled lines becoming pixelated, unless your textures were WAY too big, that is.
The other option is to use polys to make actual vector shapes. As you can see, I do make some use of that, in cases where UV skewing would not get the right result. But if you don't do any skewing and only achieve angles via poly edges, you'd have an even greater poly count than this.
So the method used on this model is an in-between of sorts. I think it hits a nice sweet spot.
One other thing to note though when working with UV skewing is that GameMaker's anti-aliasing method will work only on poly edges, not textures. So, depending on how you do things, you might get some inconsistent looking AA, unless you use a different kind of AA via shaders.
I know this is all quite off topic (which is part of why I tucked it away in a spoiler), but I just had the urge to share my findings, because I think it's exciting and that it could be useful knowledge.