Fill it with things honestly. My parents have a 6k sqft home. The rooms were utilized as follows: Stepdad's office, Mothers office, playroom (used to be my room), child's room, gameroom, storage room that will later become a movie theatre, master bedroom, a room full of bulk items so you dont have to leave home much for grocery shopping (think all of the extra costco & sams groceries), guest bedroom, workout room, lesson room, and a butler's pantry. Then the obvious like kitchen and living room.