You have a good base to start from.
First, I doubt that the Throne Room and treasure/summoning room would have the same floor tiles as the prison cells. I would put in a richer looking tile. I would put something in the throne room to decorate it like a couple statues, or big candle sconces. In the torture room I would put a small table with some nasty tools. Unless you need all those cells, I would convert some of them into larger rooms for use as guard rooms, waiting rooms, storage rooms, etc.