I like to go with classic decorations my self. I usually don't use tv's couches and the like. A good large room for entertaining guests is always nice. Of course need the suits of armor and toparies to show off. Statues and stone work is always nice if you want to go with a more rugged medievil look. Always define the rooms. A room devoted to being a stable is always a popular one. Castles have good space and tiny corner rooms to use.