The vast majority of the dragons' empire are reptilians, organized into a race-based class system.
At the top is the Pentarchy. The dragons' power, both personal and political, approaches godlike. Each dragon is unique, but can be briefly described by its niche in the empire. The Gold is a philospher-king, defining the virtues and values of empire society. The Silver is the master of masters, the greatest of scholars and craftsmen. The Bronze is the lawmaker and supreme judge. The Blue is spymaster and practitioner of realpolitik. Finally, the Green is a great hero, often leading the empire's armies, investigating mysteries, or solving problems for the people.
Second are the blooded. To be blooded means that you descend from a dragon, but this is not defined by who your ancestors were. You are blooded if and only if you manifest sorcerous powers as a result of your ancestry. If you manifest no magic, you are not blooded, even if you were fully half-dragon. Blooded are the only legal practitioners of magic.
Third are lizardmen, humanoid lizards averaging 2 feet tall, with small, beady eyes, they have great patience, a dulled sense of pain, and require little in the way of sleep or sustenance. They are the workers and soldiers on which the empire can depend.
Last are kobolds, child-sized lizards with large, snake-like eyes and great flexibility. They are noted for having no teeth, their diet consisting of small animals and large insects swallowed whole, although stews are becoming popular. They have much the same role in the dragons' empire as goblins do in goblinoid society.
The empire is a designed society. The dragons took scattered tribes, broke them, and rebuilt them. The empire has no state religion, because in many ways the empire is a religion. Virtue is defined by the Gold, justice by the Bronze, value by the Silver, truth by the Blue, and valor by the Green.