At PSR they rightly note that the Knight won´t fit onto his mount, the saddle is way to small, but that´s easily cured by cutting the back rest off :-D
The shield pattern and flag are from Luther von Braunschweig (also known as Lothar; ca. 1275 – April 18, 1335) who was the 18th Grand Master of the Teutonic Knights, serving as head of the order from 1331-35.
He most probably wouldn´t have carried his own standard but it looks better and who cares? :-D