Seems like everyone wants to skew young; Harry is pushing 40 in Changes and we've got 10 more+ years coming. That being said, here are some of the faces I see in my head.
Harry: Hugh Laurie, Hugh Laurie, Hugh Laurie
Murphy: Elizabeth Banks has always worked here for me
Thomas: Michael Fassbender, who I wuldn't have thought of without reading this thread. (Sorry Priscillie, I think Bomer is too young)
Susan: Eva Mendes
Michael: Jeff Bridges (I love the idea of The Dude being the Fist of God, and he could do it. Give him an excuse to lose the belly)
Molly: Blake Lively
Sanya: Djimon Honsou
Morgan: Alan Rickman (He can play disdain like nobody else)
Eb: Robert Duvall (it can be no other, Eb IS Gus McCrae from Lonesome Dove)
Merlin: Donald Sutherland
Nicodemus: Gary Oldman (typecast as a villian, and so what?)
Kincaid: Russell Crowe (when he's fit)
Marcone: Adrian Pasdar (from Heroes)
Ms. Demeter: Tilda Swinton (emotionally vacant, hollow-eyed weirdo)
Ms. Gard: Charlize Theron (actually, insert any tall, blonde, not too skinny competent actress here)
Hendricks: Michael Clarke Duncan (I know in the books he's white, but so what?)
Mab: Heidi Klum (anybody watch Project Runway? I totally think she could do this)
Lea: Julie Benz
Maeve: Eliza Dushku
Lara: Kate Beckinsale (so she has already done hot brunette vampire - don't fix it if it ain't broke)
Lara's sisters: Megan Fox, Jessica Alba, Natalie Portman
Mac: Bruce Willis (c'mon, you know that works)
Butters: David Krumholtz (the guy from Numb3rs)
Vincent: Eric Szmanda (CSI Las Vegas - I've always liked this guy and it works for me, alternatively he could be Fix)
Luccio: (new body): Milla Jovovich
Lash/Lasciel: Ali Larter
and...
Toot: Justin Timberlake (with CGI shrinking - I think perfect!!)