The only slight improvement I can suggest might be naming the mountain ranges? The Red Mountains, Mountains of the Moon and Frostfangs are all unlabelled on this map.
EDIT: Very minor typo. House Marbrand's castle is 'Ashemark', not 'Ashenmark'.
I can't see any other errors. DRAGON Magazine did a supposedly professional map of Westeros once and it was riddled with typos and castles in the wrong place. This one wipes the floor with it