Aslong as I have known dragons and the stories and myths around them, I always remember them sleeping on top of their gold hoard. Seriously, where else would a dragon want to sleep ? Hoard chambers should give dragons just enough room to comfortly stretch on those large hives of gold, instead of having them locked up the way it is now.
That new chamber I mentioned would be just as the hoard chamber is now, which means purely decorative without any deeper sense to it. What about a hatching chamber ? A warm cosy place with a nest and some partly empty egg shells in it Ild find that a really cute thing to have in a lair.