Well, in viking culture (and don't kid yourself by saying Nords =/= vikings, you're technically right, but philosophically wrong) slaves were a part of everyday life, but it wasn't a racial division as it was in early America or for instance Morrowind. Slavery was basically what happened to you if your parents were poor (I think you could sell children to pay off a debt) or if you were captured in war. Reports from the time, however, state that slaves were treated with a fair amount of respect, even kindness (not justifying or forgiving it, but that was the attitude, if sources can be believed, unlike in MW or other historical contexts were slaves were harmed as little as possible only to maintain their value)
Perhaps instead of starting off as a prisoner in jail, you could be the "captive" slave of a cruel master you kill, or even a kind master who sets you free on his death.
As far as the caste system goes, medieval Scandinavia (as I recall) was fairly stratified but also socially mobile. There was a democratic council called a Thing, where every free man had a vote. Social status was often displayed by a torq ( horseshoe shaped metal ring) around the neck, iron for slaves, copper, silver, and gold as you ascended the social ladder. That may have been for women only, I forget...Gallic males wore torqs in Ceasar's time.
Partialy correct but I wanna point out one thing, I'd like to remind you that even though there were no "black" slaves back then there was a bit of raceism. The word "Slave" acctully comes from the word that the "Vikings" used to call Slavs (polish and other slavic country folk). The Scandinavians were held as the greatest warrior but many people even as far as the arabs in the middle east would higher them to fight in there most inportant armies. The was a bit of racial stigma associated with that which would later be the basis for the Nazis but they would also pride anyone who could fight like a true warrior, cause for them might did make right. Like in the story i shared erlier. That man was a Pol i believe but her later was free interily and respeced
As for the other part right on, they were pretty democratic in that everyone had a fair chance for hte most part. Women could own property, vote if they had no husband, they could keep there own property in marriage, and could seperate from there husbands if they wished and had good reason, though when it came down to things there was nothing the prided more then war so when it came to decide who was right in such a thing it came down to a fight to the death cause if you were victorious you had Odin on your side. For the most part slaves were given the basic nessesities and treated somewhat civial (for the time at least).
Oh though Gallic =/= Norse , thats like saying modern day Americans = British