Hmm good point. I think it depends on the type of Slavs, Baltic Slavs and Slavs from Northeastern Russia I'd group with Northern European and Balkan Slavs I'd group with Southern Europeans. I was talking about splitting Europe into North and South, not the actual region of Northern Europe. Thinking mainly from a aesthetic point as well.
Not sure what you mean by Baltic Slavs - if you count Russia separately, that leaves only Poland. You were probably thinking of Balts (Latvia, Lithuania).
Estonia could be grouped with FInland as they have the same ancestry. It's true that no race in TES is based on Slavs, but West Slavs could probably pass for Imperials. East Slavs as Nords? Well, if you think of all the mead and drinking contestes, yeah, maybe

But otherwise they don't have much in common with Scandinavians.
And South Slavs are in no way Imperials.