Was that Hvitserk being led in chains before Ivar and his bride-to-be in the ending ceremony?
Hard to conceive of who else it could have been, there are no other real candidates.
After that build up it'd be dumb if turned out to be just some random nobody. So if they were going for the suspenseful cliffhanger by concealing his face it sort of fell flat.
Edit: On further reflection, I seriously doubt it's Hvitserk and is most likely some random nobody Ivar's demanding as a godly sacrifice to him. But I still hate cheap tricks of cliffhangers like this.
Edit2: Ok, my best guess now is that scene was a nightmare premonition of the Seer's that we see him wake up from in the very last shot. A random person would make no sense. Sacrificing Hvitserk also wouldn't make sense in light of Hvitserk warning to Ivar earlier in the episode that he was also a son of Ragnar and asked him what he thought the people of Kattegat would do if Ivar harmed a hair on his head.
If that was Hvitserk being a little too full of himself, I think Ivar would have stood his ground. Instead he backed down from Hvitserk's challenge and suggested he consider leaving with Harald.