Doesn't work for me; I still see Morgan as Rutger Hauer in 1984 or so.

It's these guys for me:

Harry- Paul Blackthorne.  Was perfect casting imo, about the only thing the tv show did right.

Murphy- Murphy is Laura Linney for me.  If only she could become 5-10 years younger for storm front!

Thomas- I've always pictured the white court as the flawless china doll type.  For me he has always resembled Jude Law...whats more, Law could pull off the effortless swuave thing.

Morgan-- I don't know why, but I've always pictured him as kris kristofferson.  There is that mix of venom yet you know underneath he is one of the good guys.  He had that 'been there, done it' vibe going in blade too.

Lara Raith-- Mila Kunis or Megan Fox.  If they wanted her slightly older, Angelina Jolie or Monica Belucci.  This character just needs to ooze sex and power.
Susan-- Roselyn Sanchez
Bob -- Voiced by Stephen Fry.  Needs the sarcasm and the wit in the voice.   Would be superb.
Butters-- Needs the geek factor.  I think Zach Braff would be great as butters.
Michael--  Needs a severity, but also the ability to really act out such a pure character.  For me he would be great portrayed by Viggo Mortensen.

Nicodemus -- Has always been Udo Kier for me.  Seriously, google him.  He has the total look, with an otherworldly presence about him.   
Kincaid --  I've always pictured him as Benicio Del Toro.
Faerie Queens-- Think it would be fantastic to have Cate Blanchett portray both.