@Damiann47 Yes, they don't. As an Unknown, you can be any nationality, provided it's still plausible, meaning that in addition to the five provided, Russians, Poles, Lithuanians, Estonians, Latvians, Belarussians, Ukranians, they are all allowed. You also can be an Unknown mage, though of course you would follow the rules of Finnish mages. 

However, Unknowns would not have large groups or governments. Any settlements would be temporary or nomadic/semi nomadic, with groups not exceeding 15-20 people. They would be close knit, family-tribal groups, much more primitive than the Nordics, without electricity, literacy, running water, or a permanent source of food. They would be hunter-gatherers, migrating north and south with the seasons and following animals. They would also all be Immune, but very much aware of the dangers Beast, Trolls, and Giants pose. Timewise, if the Nordics were pushed back to the 1930's, then these guys were pushed all the way to BC. 

So, in terms of restrictions, they don't have to have a scandinavian name, they can be any plausible age (i swear, if you play as an infant, I'm feeding you to a Troll), Any nationality (In places which have silent world. Danish, Icelandic, and Norwegian don't have very much, if any, so they aren't possible), Speak any language (Again, only those plausible, you ca't be a pole and speak fluent Icelandic), any profession, provided you can do it without electricity/heavy firepower/organized society, and any pet, as long as you remember the rates of immunity.

I hope that answers some questions :)