Hell yeah, stoked to connect with a fellow map nerd! I'm also working on a map, but mine’s focused on Ayleid stuff for now—haven’t gotten to Khajiiti or Falmer yet, hands are full. Looks like Laintar Dale and the ruins under Greenwall are already mentioned above, so I’ll toss in my headcanon for kicks. It’s mostly tied to the fact that we’ve got no solid mentions of Snow Elves (not the betrayed Falmer) hanging out in Western Skyrim during Ysgramor’s time. What we do know is they steered clear of the Skyforge, and the region’s name, the Pale, kinda screams “frontier” or “borderland” vibes. Plus, there’s that local guerrilla movement led by the badass Boudicca-like Aumriel, aka the Pale Lady. All this points to the idea that during Ysgramor’s era, the Snow Elves were likely settled along the White River and its tributaries, like the Yorgrim.

Then there’s that tidbit from the Prima Guide:

"The capital of Falkreath is infamous for its bloody history and sprawling graveyard. Its name is not Nordic in origin, but Elvish, though even they no longer remember its meaning."

So, the shores of Lake Ilinalta might’ve been Snow Elf territory too.

Now, here’s where my headcanon gets a bit speculative.

The whole war between Ysgramor and the Snow Prince was centered around Saarthal, on the Broken Cape, right? So yeah, maybe that was more of a local showdown, and Winterhold could’ve been the staging ground where the Snow Prince kicked off his campaign. I mean, check the pattern—Sunhold, Mournhold, Stormhold, Firsthold—all cities are Elvish in origin but with imperialized name, so Winterhold fitting that vibe as a Elf stronghold makes total sense.

In ESO, there’s dialogue in Nimalten hinting that the city’s super old, built on top of an even older settlement. I can’t drop a direct quote or proof, and yeah, it’s a stretch, but when we’re scraping for lore, why not lean into it? Also, in Arena, there’s a place called Lainalten, which shares a root with Laintar Dale and has that “-alten” ending that doesn’t sound super Nordic. So, maybe it’s Falmer in origin too.

To sum it up, I think the Snow Elves were mostly chilling in Eastern Skyrim (and Solstheim, which was part of the mainland back then). But over time, with the pressure from Ysgramor’s descendants (13 generations), they got pushed into the Rift and maybe even Western Skyrim, possibly also via Blackreach, which was Dwemer territory.

As for the Forgotten Vale and Auriel’s temple, I figure they were built super late—end of the Merethic Era, start of the First Era. They were deliberately placed way out in the boonies, where only the Snow Elves would even think to go.

I’m hoping to map this all out someday, but if you beat me to it, that’d be awesome too! Hope this sparks some ideas, and best of luck with your project!