The Gray Mountains are currently not much different from the other mountains. That’s why I think it would add a lot to the game if it had dragon caves in it. These caves would be large, spherical structures deep in the mountains. Their bottoms would be completely covered with piles of gold and silver. It would also contain 1-3 chests containing silver coins, cups, dwarf and rohirrim equipment. Of course, due to the many treasures and the small number of dragons, they would be very rare structures.
Sorry for word repetition, I'm not English/American.