When you resurrect the old breeds, can you post screencaps of them?
Also, the texture for the armor on the mobs looks kind of flat. Maybe you should talk to some willing to aid you with that?
Leo, BTW, I have not seen lag that can be attributed to the dragons. If you are having lag on multiplayer with them, it's probably because it's loading new chunks. I'd advise pregenerating the map a bit.