I picked out Elsa as my princess because I liked the fact that she is not perfect, 100% good or 100% nice. She is flawed, insecure, does not always make the right choices. In part, she is the bad guy in her own story which is very different than the traditional fairytale heroine.
Once I had her as my inspiration I tried to answer the question; where did Elsa get her powers from? And who were her ancestors? How did they get their powers? It was easy to decide that Elsa's ancestors were the Vikings and her great great great grand mother, High Queen Älsa, made a deal with the troll king to have ice powers to defeat her enemies. She was a warrior, after all. There I got the inspiration to look for characteristics of Viking women as warriors and I stumbled on to many pictures of Lagertha from the TV series Vikings. Lagertha's braided hairstyle and frigid beauty fit this world very well, as did the Valkyries, a perfect inspiration for my warrior queen.