I am extremely familiar with Westeros both in the time of Ned Stark and in the time of Eg and Dunk. Read the books, short stories, graphic novels and current on the series. I would prefer a game not in post Roberts Rebellion time frame. I am working on a story (for a game) pre-Blackfyre Rebellion, that seems like a time that can truly be explored and exploited using the outline Martin has laid out. Having said all of the above if you are less familiar or would want to change details of history, that's fine too.