The castles here and throughout the series are large, sprawling stone structures with battlements, moats, drawbridges and portcullises. In fact, most of the real castles depicted (Winchester, Lincoln, etc.) would have been simple wooden motte-and-bailey structures at the time. Round stone towers were unknown in England during Stephen's reign.
When King Stephen awakes from his nightmare in the dead of night, there is a full, roaring fire in an open fireplace. All fires would have been extinguished at bedtime and never, ever have been left unattended. The risk of the tapestries and wooden beams catching fire was too great.