When you speak of culture in Skyrim, I imagine a dining hall full of nords with mead and food piled up, loud and boisterous. Then imagine one of them beginning to bang the table to http://www.youtube.com/watch?v=mK1jbzMyFeU beat. They begin to all join in and begin to chant. Then they sing the chorus, and the king that was sitting at the head of the hall stands up, proudly taking in their song.
Sorry, when I picture Nords, I think "vikings." I'm pretty sure that that's not very accurate, but it definitely makes me pictures vikings in a mead hall, a loud and boisterous bunch, who take pride in independence and strength, and hold great respect for their leader (if he's a good one anyways.) I imagine a nord that isn't bothered about speaking his mind, and that a good thumping is better to resolve problems than any kind of negotiation.
This is what a viking culture seems like to me, and even if Nords aren't exactly like vikings, I would GLADLY see the same kind of depth in culture in Skyrim. Hell, the scene described above alone is enough to make my cry in utter amazement and die.
Either way, I hope that the depth of the culture is much better than the previous games, it would make an epic game become godly!
Some Nords are clearly like the Norse of our own history, Bloodmoon and Bruma reflect this, as do quite a few of the Nords that we have met in the various games. But there is (apparently, we obviously won't know how the game really treats this until it is out) quite a bit of wealth, civilization and power in Skyrim.
One influence I would like to see in creating parts of Skyrim that still tend towards the edgier side of Nord culture would be the Klingon Empire as seen in Star Trek, the Next Generation. That sort of blood and honour mentality mixed up with politics and intrigue made for some of the best episodes of the show, and it could really be cool to see that sort of thing in TES V.