Well, it's pretty obvious what Sovngarde was based on, Valhalla. But who's Sovngarde's version of Odin?

I'd say Shor.

That would probably be Shor.

Anyone know what he looks like?

Don't know that I've ever seen reference to a depiction of him in humanoid form... seeing as how he's the Nord equivalent of Lorkhan, the "Missing God," I don't think you could find him even if you knew what you were looking for.

http://www.uesp.net/wiki/Lore:Gods_L#Lorkhan

However the moons of Nirn are considered his "corpse" so maybe that's as close as we can get?

Oh, so he isn't so much based on Odin then, 'cause there's paintings of what they thought Odin looked like. I saw they also described him as a Trickster in the link, so maybe he's a cross between Odin and Loki?

The elves think he is a trickster.

He's Shor, he's Lorkhan, he's Shezarr... but he's not necessarily a carry-over to the TES universe of any particular mythological figure(s) from our own traditions. He's going to be like some of them and unlike some others because ultimately the ES universe is a product of and reflects the same human spiritual imagination that gave birth to our own mythological traditions, which all share some common archetypal foundations and those do carry over because it's inevitable that they would do so. Obviously the Nord culture is influenced by our Norse/Viking/Teutonic traditions and style but I wouldn't go looking for a literal equivalency between the pantheons.