First post - although I registered a few years ago and have been lurking irregularly ever since.
My wife and I were just discussing casting details and came up with one that I don't think has been suggested:

Harry Dresden - David Walton.  (Plays the lead character in "About a Boy", where he snarks it up with aplomb.  He's also tall (6' 4"), which helps.


For Thomas, she's adamant that Ben Barnes is perfect.


For Karrin Murphy, I too have to go along with the Kirsten Bell idea.


For Butters, it has to be Jay Baruchel


With Michael Carpenter, we're going for Hugh Jackman (as per others here), although an honourable mention for Gerald Butler


For Charity Carpenter, Lena Hedley (from Game of Thrones, among others).


For Nicodemus - Benedict Cumberbatch has the ability to swing from charming to malevolent so, so well.