Hopefully not stretching the definition of Castle too much, but I'm sure I read that anything up to the Great fire of London (1666 fact fans) was acceptable.
My two entries for the realistic castle figure category are Queen Elizabeth I (who reigned 1558-1603) and Sir Francis Walsingham, her principal secretary and 'spymaster'.
CCCX - Queen Elizabeth #2 by andhe , on Flickr
CCCX - Sir Francis Walsingham #1 by andhe , on Flickr
Queen Elizabeth 1558-1603 by andhe , on Flickr