Yeah, I'm putting any post related to Supernatural under this. I could do TV and movies, sure. But this is funnier.

Anyway, after getting bored and doing a little bit of random digging... Cas's true form is the size and height of the Chrysler Building. That, and because he was promoted to Seraph/Seraphim, his form would have six wings covering himself for the most part instead of just the two. Otherwise, his body could be an eye, a head, an animal, an animal head, or just something that looks like a human.

Also, Misha's little "Cas's wings are rainbow" would be so funny in this context. Personally, I see them as black because of how they are in the show, and he's considered a fallen angel. But can you imagine this 1,046ft(319meters) 6-rainbow-winged (I'll just say human figure in this case) human thing hiding itself and its body while blinding and killing everyone in the area due to how powerful and bright it is? Apparently, that form must also be hot according to Cecily.

Also, according to the trivia, "After becoming a "mutated angel" by absorbing all of Purgatory's souls, the wing flapping sound is no longer heard when Castiel teleports, insinuating that it affected his true form." Imagine Seraph Castiel with some sort of mutated true form at full power. No thank you.