Okay, I cast the movie and assuming I could get these people for an affordable price

Harry-  that's toughest really, because you need a really strong actor who's tall and rangy,  a younger Peter  Coyote mabye   but I'd choose Eric Bana or maybe Christian Bale

Murphy-  she'd be a little voluptuous but I really like Christina Ricci in that role, short, and does badassed very well with a bit of sweetness. 

Thomas-- Brad Pitt.  No contest here.
Morgan-- Alan Rickman    You need menace.  the problem is that before Turn Coat Morgan has few dimensions.
Lara Raith-- Nicole Kidman
Susan-- Rosario Dawson
Bob -- (voiced by John Goodman)
Butters-- Steve Buscemi or a young Wallace Shawn. Okay he's too old but what about Paul Reubens, who might be gettable.
Michael--  he's particularly tough because the actor must pull off Dudley Do-right without going over the top. He needs to  be underplayed.  Steve McQueen would have been perfect but he's too dead for the role.  okay, I'll go for Russell Crowe, who's versatile enough.  Or Gary Oldman.

Nicodemus -- Christoph Waltz--- have you seen inglorious basterds?   
Duke Ortega--  Benecio del Toro
Kincaid --  George Clooney
Queen Mab-- Lena Olin
Aurora-- Scarlett Johansson
Maeve-- Thora Birch (Christina Ricci being taken)
Madrigal Raith -- John Cusack
That's enough for now.

Marcone: Ray Wise
Dresden: Clive Owen or Christian Bale (Really liked that one!) Maybe Hugh Laurie (if we're going older)
Molly: Amanda Seyfried
Murphy: Jessica Marais
Thomas: Jude Law
Susan: Eva Longoria
Morgan: Alan Rickman (would be funny... the man's a genius!) or Ian Glen
Lara Raith: Olivia Wilde or Marena Baccarin
Butters: Anthony Rapp
Ebeneezer: Bruce Willis
Michael: Maybe Sean Bean?

That is all!

Be an actor for a day. Take a few scripts (or books from 1st POV) and read them out loud to yourself (or a friend who won't think you're weird). Try using different voices for the characters. Make your voice high or low, grovelly (did I spell that right); speak fast, slow, according to how you think that person might sound.

It will help you get some perspective on how you'd like your own characters to sound. I throw in accents on my own characters in my head.

This Idea doesn't work for everyone but it may be the thing you need to help make each character and chapter special. 

I don't know if this question has been asked yet but:

What is up with MAC? Don't get me wrong cause I think he's all sorts of hidden bad assery underneath the layers of two word sentences. I just want to know if you have awesome plans for him. I don't need specifics or spoilers, just a yes or no will do!  thanks!