I think it's okay to have extra space and empty rooms, but suggestions:
- Library that's two floors
- Art rooms
â—‹ Recording/streamer/video production studio, music studio, photo studio, dance studio
- Theater
- Sauna
- Indoor Pool
- Gym
- Game Room
- Conference Room
- Dressing Rooms
- Vault/Safe
- Rooms dedicated to the family's eccentricities (for example, if someone is into collecting X, there can be a room full of that or a room for a certain hobby)
- Tatami Room* (I doubt this will fit the aesthetic of your castle, but I'll just throw it out there - my Sims kind of have this in one of their homes)
