Some successfully reported parings are:
To breed a seasonal dragon you have to in clued these tree elements:air,fire and plant
Sonic Dragon and Flower Dragon
You don't breed a Kairos Dragon in DragonVale. You have to get parts to complete it.
Blazing+plant
you breed a ice dragon with a mine dragon
You have to breed a plant and a fire dragon.
As of July 2012, there has not been a star dragon in DragonVale.
You have to breed a sun and moon dragon together
You have to breed a metal and a water dragon together.
You have to breed a plasma dragon with a salamander dragon.
Never it's not limited
Breed the earth dragon with the fire dragon.