The piano is actually there because we needed a ballroom to entertain some NPCs for a political summit. Several of the servants in the mansion were skilled in instrument use, so we made a small area for performers.

The Dragon Skull is in the sand of a fighting/training pit for the party's fighter. She basically took out a red dragon single-handedly during one of our adventures, and it's a replica of that dragon's skull that we couldn't take away as a trophy because the dungeon collapsed.