Two members of the cosplay group StarMints — Sweet and Cherry — dressed as Frozen’s Anna and Elsa with a twist. They did a Viking-inspired redesign of the costumes. They specifically pulled from the looks in How to Train Your Dragon. The Anna costume, by Sweet, looks a lot like Astrid from that film. They made the mash-up from the ground up for a convention (and won third place in a costume contest). The ensemble involved a whole lot of hand-painting patterns and swirls on fabric. You can see the result of that tedious work in pictures below.
See more in progress photos and viking Elsa in this Facebook album.