Just a comment - the castles are way to big =(
But some details that would be nice would be possibly little statues of all the old rulers
Maybe I'm a little biased, being an old ruler myself, but I think having a hall of rulers would be sort of cool =)
Why not add some NPCs? I know you personally probably cannot do this, but that would be nice.
As for other details, you should add some wall tapestries