I know next to nothing of Skyrim lore, so could someone tell me if Sovngarde is purely a Valhalla for Nords or can other races like Elves be admitted?

This article seems to suggest that it's only a Nordic afterlife, barring special circumstances, and TES is full of special circumstances.

Link removed: Broken.

Dat wiki ain't welcome here.

That, and your link is botched on my end. Anywho, most likely not, unless in a few exclusive cases (In the case of Skyrims Dragonborn), but for the most part, no. Many Lorkhanic avatars have this thing against Mer you see. Whether or not its occupants give a hoot is another matter.

To achieve a dramatic parry and riposte in this debate, this: http://www.uesp.net/wiki/Lore:Sovngarde

Says pretty much the same thing.

If an Elf is born a true son of Skyrim and dies a true son of Skyrim and can valiantly fend off Tsun, then I see no reason why even Ysgramor wouldn't welcome them into the glorious hall.

Wouldn't only Nords be considered true sons of Skyrim? I tend to lean towards a yes on that, being that Skyrim is the home of the Nords and all. I would believe the "Sons of Skyrim" applies to lineage more than where you were born. Therefore, even if you're born a Nord in Morrowind, you're still a son of Skyrim, and being born in Skyrim doesn't make you a true "Son of Skyrim" if you're not a nord.

You only need the heart of a Nord to be a child of Skyrim. If you would fight and die for Skyrim is all that matters.