Long before the rise of Valyria, Westeros was divided into countless Petty Kingdoms. In the south, the Reach is consumed by fire as weak kings are set upon from all sides, and strong ones vie for their remains. In Dorne, the deserts run red with blood and in the north four kingdoms struggle for supremacy, even as they face invaders from all sides. As chaos descends upon the lands of Westeros it remains to be seen which Kingdoms shall forge dynasties to last a thousand years, and which will fade into history.
Why can't you use the Bolton sigile from the TV show? It's much more epic, better looking and practical. Pink and purple colors were insanely expensive in the middle ages and only those in top classes could afford them, but in GRRM universe a common Bolton soldier has no such problems, apparently... :D
What you say is right, but there are just too much in this universe that would be terribly expensive or just impossible in the real medieval world. I agree that the show's Bolton sigil is cooler, but in my opinion the mod should stick to the books instead of the show. What shocks me also in this universe is the total absence of any real rules of heraldry, like some color don't go with some others in a sigil and so on.
So let's just pretend that in the North grows a very common flower that gives pink pigments and roll on with it ^^