Cosmos
Ventus
Phaeus
Necros
Terros
Khaos
Pyros
Baryos
Vitas
Solaris
Chronos
Hydros
I like the vast majority of those, although I'm not a fan "Phaeus" or "Baryos". I'd change Darkness' god to "Null" and gravity's god to "Colossus". Other than that, those are really cool.
Just because I feel like it, backstory for all of them.
Cosmos - The one beyond the sky. The aether in the land of elements is limited, but beyond the sky, the stars are limitless. Cosmos looks down on the other gods.
Ventus - He who is free. Ventus enjoys flight so much, he ignores the rest of the world and floats where he pleases. Ventus ignores the other gods.
Null - The Vengeful. Not considered a god by the others, Null was excluded from the Dieties. Null blessed the world with a place to hide, wait, and strike. Null lurks the other gods.
Necros - The Death Bringer. Necros is a merciful god, helping the dead on their way as though they were his children. Necros is married to Vitas.
Terros - The still one. Terros is slow moving, stable, afraid of the destruction of the land. Terros is cautious of the other gods.
Khaos - The bringer of change. Khaos is eccentric, chaotic, and insane. But there is a method to his madness. Khaos baffles the gods.
Pyros - The Passionate. Pyros is confident in everything he does, and does it with a fury. Pyros eggs on the other gods.
Colossus - The keeper of peace. Baryos is calm, collected, contemplative. He's slow in what he does be he's never wrong. Colossus understands the other gods.
Vitas - The Life Giver. Vitas is a merciful god, granting life and beauty to the living. Rebirth and healing our her grace. She is married to Necros.
Solaris - The Illuminator. Solaris considers himself the leader of the gods. He graces the world with light, clarity, and law. Solaris guides the other gods.
Chronos - The one beyond the flow. The time in the land of elements is cruel, but beyond it's flow, the possibilities are limitless. Chronos structures the other gods.
Hydros - The Calm. Hydros is wary of everything he does, and he does it smoothly. Hydros chills the other gods.
The opposites work well too.