Figured I'd join in on the fun.
I read through the demo again to make sure I had all the physical descriptions @Rohie gave for the characters, while trying to keep the gods as diverse as possible, and this is what I came up with:
APHRODITE: Song Hye-kyo
She's Korean, and stunning.
DEMETER: Kerry Washington
Do I have to explain this one?
DIONYSUS: James Franco
Just look at him and try to tell me that he wouldn't be a fantastic Dionysus.
PERSEPHONE: Kiersey Clemons
Is she super identical to Kerry as Demeter? No, but they do look similar, and she would be perfect as Persephone.
APOLLO: Sam Claflin
I admit I got a little lazy on this one, but he still fits really well. I can picture him riding a sun chariot (not in a sweater, obviously)
HADES: Dominic Rains
Dark eyes? Check. Dark hair? Check. Looks sad, compassionate, and serious? Check. Would look like a bad ass with an army of skeletons and ghosts? Check.
POSEIDON: Jon Hamm
He has green eyes and a beard, and I can picture him holding a trident and looking at the Bearer with this face when they walk in.
ATHENA: Angelina Jolie
She just looks intelligent. She always looks like she could be up to something, but her face still has this softness to it that would make the Bearer trust her a little bit.
HERA: Beyoncé Knowles
Okay, hear me out on this one. Just look at her. Can you picture anyone more worthy to sit beside Zeus as his proud, jealous wife? I bet you can't.
ZEUS: Richard Armitage
He looks mature, but still attractive enough to have a bunch of mistresses. Also looks like he would have no problem electrocuting anyone who gets in his way.
ARTEMIS: Aiysha Hart
She looks carefree and young, and I can picture her leading maidens through a forest, and scolding her brother.
ARES: James Purefoy
I don't know why I automatically think of this actor whenever I picture Ares. Probably because he played a serial killer in the Following, and can look neutral or sinister depending on what's happening. Also he looks good holding knives. His eyes look kinda black in this picture, but this was the one that best captured him.
~EDIT~ If I didn't use James as Ares, I'd use him as Kronos.
In his place, I think I'd use Jason Momoa, who I considered originally, but I didn't choose because I didn't want Ares to be the stereotypical strong and angry dude. I wanted him to be more subtle. But I know conventionally, that's how Ares is pictured, so here he is in all of his manly glory:
HEPHAESTUS: Dev Patel
Looks clever, and looks like he would rather be in his forge than anywhere else.
HESTIA: Willow Shields
~EDIT~I COMPLETELY FORGOT ABOUT HERMES!!!
HERMES: Matt Bomer
He's cute, and he's got a mischievous smile. In American Horror Story, he proved he was more than just a pretty face, and was able to convey the darkness that the show demanded very well. This would come in handy, because from what I've read so far, Hermes is capable of being comic relief, and also a force of destruction.