dph,
you know what  could provide a nice firelight glow to the room. IDL lighting. Just create a couple props.  red, orange and yellow over in direction of fireplace. turn ambiance up to like say 6  if they are not too far away. you'll have to test it based on your scene. then delete and/or turn off all lights. turn on IDL lighting manual render settings.
 only possible in Poser 8 or Pro 2010 though... It will produce a very nice natural feel to the light.
regards,
jason-