Grace Speaker wrote:Newton P - Kris Marshall or Richard Ayoade,
RA would be a BRILLIANT choice - I'll kick Kris Marshall off the bench

Beelzebub/Dagon and Brother Francis - Andy Serkis, although he's probably too expensive, so Stephen Mangan would be good as Brother Francis
Stephen Mangan would be another good choice for Crowley
Nanny Ashtoreth - Michelle Gomez (Missy in Doctor Who)
Or indeed Sue White in Green Wing - from which I notice you have a lot of your choices

Death - Charles Dance
Or Ralph Fiennes
Famine - Stephen Mangan or Ryhs Irfans
Tall, skinny, saturnine - possibly black - there's an American actor I'm thinking of but can't place...
War/Carmine Zuigiber - Rosario Dawson (with her hair dyed auburn or just in a wig), the woman is drop dead gorgeous
Well, OBVIOUSLY we want Summer Glau for this one, but ...

Another good choice would be Sian Brooke
Pollution - not sure on this one, but Laurence Fox maybe?
I think Bruce Langley (Technical Boy on American Gods) has the insane aura for this one