I hope it's cool to resurrect this thread, my first post on this board *waves*. Based mostly on looks, and I know this is more Hollywood than the HBO series could ever be, how about these suggestions:
Jaime Lannister - Josh Holloway
Edmure Tully - Ewan McGregor
Roose Bolton- Christopher Walken
Ramsay Snow - Cillian Murphy
Asha Greyjoy - Mila Jovovich
At one point Cersei = Nicole Kidman, Stannis = Daniel Day-Lewis, Kevan = David Ogden Stiers, but that was almost 10 years ago and I think they're too old now! But maybe make-up would help and if this happens I bet everyone will be cast a little older anyway.
Really like these:
Lyanna- Natalie Portman (though a young Jennifer Connelly would've been perfect!)
Sansa- Rachel Hurd Wood
Tom Welling- Renly
Joffrey- Max Pirkis
Balon Greyjoy- John Noble
Lyn Corbray- Hugh Dancy
Lady Taena- Catherine Zeta Jones
Bronn- Hugh Jackman
Vargo Hoat- Steve Buscemi
Loras Tyrell - Orlando Bloom
Melisandre - Monica Bellucci
Tywin Lannister - Patrick Stewart