If we're talking about new questlines, mod Falskaar gives whole new area to explore with new, non-canon quests. It's nearly dlc-sized. I dont have it myself, but its one of most downloaded ones, so it can't be bad.
Realistic Needs and Diseases, i believe, would make a nice role-play combination with Forstfall (that Joe mentioned), if youre into that sort of thing.
Mods like Cloaks of Skyrim and Winter is Coming add, well, cloaks. And it really fits into land where average daily temperature is -15℃. They also make use of things you found useless until now, like linen warps, snow bear pelts, etc.
Get all 'em daedric artifacts. Never enough of them. Try unlocking every shout, if you hadn't done that already.
So many things to say, I'll leave it at this, lel.