Antonyms of furniture:
built-ins, fixtures.
Examples of usage:
  1. But I know lots of the ladies has pieces of that furniture; and most of them would be mighty glad to get rid of it.
    "An Alabaster Box", Mary E. Wilkins Freeman and Florence Morse Kingsley.
  2. Raphael, tell me, did no one advise you about the furniture of your hotel?"
    "The Magic Skin", Honore de Balzac.
  3. They lived for a time on the only capital they had- the poor furniture of their room.
    "Mary, Mary", James Stephens Commentator: Padraic Colum.