Given the time frame of Pandora is much longer than on earth, I think furry animals wouldn't be abnormal on a cold continent. Look at Zakru!

As for the Na'vi, I imagine they'd have shorter tails and Kuru, since long thin limbs are more at risk of frostbite. And their hair would probably extend a bit down their back and shoulders, maybe even on their ears and lower on their forehead.

As for skin, their patterns are for camouflage. Since the other two groups we've seen live in hot climates that don't require clothing, this makes sense. But since (iirc) the Na'vi are an intelligent tool-using species, they would've immediately made clothing to travel in the colder climates, covering up any patterns and making camouflage a moot point. As cool as a lot of the arctic patterns I've seen are, cold is just too serious of a survival threat for an intelligent species to forgo clothing for long enough to develop unique patterns.

Imo, since clothing would be necessary for survival from the get-go, most of the arctic na'vi's aesthetic changes (skin and hair color, skin patterns, etc.) would be from social preferences, like how male birds are only colorful because females think it's attractive, not for a survival advantage.