This is character design practice, basically. The visual aspects of the particular species I'm working with (which I'll get to in a moment) pretty much force me to work with little more than a silhouette, so I have to come up with distinct silhouettes for each individual of this species - which character designers have to do anyway. Granted, the differences are a TAD exaggerated, but it's still a fun exercise. I should do this more often!

Anyway, I'm nowhere near the first to come up with the idea of space-dwelling dragons, but this is an idea I've had for a while. Originally they looked like weird T-rex/lion hybrids with jet plane wings, but I recently reworked the design to make them look more alien. Even though you can only see their heads here, I think I succeeded.
The head-tentacle-dreadlock things are the species' equivalent to a lion's mane; they're basically there so a viewer can quickly tell if a dragon's male or female. Males have them, females don't.

Antares (top left) is the main character of the story he appears in. His body shape is very feline, though his head shape is closer to a skink or a gecko. He's meant to look more cute and less dangerous than the others, to reflect his personality; the fact that his name roughly translates to "opposite of Ares" should give you an idea of what he's like.

Tucana (top right) is Antares's brother. He's named after the Toucan constellation - I am not joking, it's an actual constellation - but he might as well be named Ursa Minor, honestly. As you can probably guess, his head shape is meant to evoke a bird's head.

Xiphias (middle left) is an elder dragon. He's named after the former name of the Dorado constellation, which is basically a swordfish; this is why he has a long muzzle. I mostly styled his head after a crocodile, though.

The other two are just some random ideas I haven't put names to, and the fish is a fish.