Opposite words for furniture:
built-ins, fixtures.
Usage samples:
  1. The poor furniture was in place.
    "Carolyn of the Corners", Ruth Belmore Endicott.
  2. Decorative Furniture and Carved Wood- Work.
    "The Great Musicians: Rossini and His School", Henry Sutherland Edwards.
  3. Just as he was trying with his own hands to help a peasant to change the position of that piece of furniture, the landlord, a Frenchman, entered the room.
    "Fables for Children, Stories for Children, Natural Science Stories, Popular Education, Decembrists, Moral Tales", Leo Tolstoy.
  4. Why should not every room of every house be covered with pictures where it is not covered with furniture?
    "Cole's Funny Picture Book No. 1", Edward William Cole.