Juliet Marillier Oficial FB fanpage many actors were suggested to play the different characters.
Here is a summary of what has been suggested. Comment if anything is missing or to suggest more.
Saga of the Light Isles
The Bridei Chronicles
EDIT: Nerwen Elendil has created an website for this, with galleries for each book with the actors suggested here. Go see it!
EDIT 2: Actors in need of role here.
EDIT 3: Another blog has been created to vote in the characters: Casting Sevenwaters. It's slowly coming live. The characters in this blog which name is a link, direct to the voting page.