I don't know what your plans are for adding new creatures, but I have some ideas for passive (aggressive when attacked) wildlife from the real world's northern climates:
Muskoxen, caribou, reindeer, moose, arctic foxes, and waterfowl such as swans (I don't know how possible it is to have waterfowl, aka birds that sit on top of the water), and otters and killer whales. Having some of these creatures in Skyrim would add a lot more interesting diversity than just bears and wolves.
There is much more diversity in the forest than bears and wolfs..peaceful and agressive creatures.
For that forest it means bears, wolfes, forst boars, wild hogs, rats, spriggans, trolls, werewolves, wargs, deers, rabbit, squirrel, moose and goblins.
You see only 1 or 2 cells of a forest that will have the size of Solstheim.
Arctic Foxes would be cool, but I've never found any resource and I've never modeled a creature or animated it.