I expect it to be fairly minimalist like with Morrowind and Oblivion's covers, but I highly doubt it'll be particularly cold or in pursuit of that "icy" motif. If Bethesda is already just as bored and frustrated to death as I am by the whole,
"waaah Skyrim will just be snow I hate the cold!" entourage we have going on here on the forums, then I think it will go for a more natural look.
Instead of Morrowind's more rustic guidelines that gave it a "frontier" feeling or Oblivion's horrendously imposing and over-dramatic molten lettering, I think the Skyrim wording would be a bit more natural-looking. I imagine a nice Celtic/Scandinavian looking font, nothing too fancy or stylized, but it would be fairly vertical and diligent looking. It would have the air of nature or some sort of supernatural, spiritual Pagan energies about it, perhaps appearing organic and asymmetrical like a plant or radiating some sort of nifty aurora borealis around its edges. A stray icicle or two could be seem forming on its bottom edge and a light, glimmering spray of snow would sit atop it.
The borders of the box would be a more inorganic Norse motif, embossed metal or a stone trim of some sort. I imagine animalistic symbols stacked on top of one another (like in a totem pole hierarchy) to the top right and bottom left of the main text.
Of course, this is all assuming that we
will be seeing Skyrim in an Elder Scrolls installment some time soon.