I know this is a major typecast that I'm doing here, but what about Clive Standen
(Rollo on Vikings
) as Skurge?
I know he's not as massive as some other suggestions here, but he's great as the ambitious, wants-to-be-the-alpha-male brother on Vikings
...And while I'm unimaginatively fan-casting people from Vikings
, how about Katheryn Winnick for Valkyrie. (EDIT: Just looked at some non-Vikings pics of her. She could totally be Amora, too.)