[EDIT] Four more characters added :D; go take a look.
The Berceuse de Minuit Character Soundtrack!
Dragomir Hirlea - Hirata Hiroaki
I chose Hirata Hiroaki for Dragomir because...he's awesome. XD;; He isn't so deep that his voice is crazy, but it isn't girly, either. He's really nice and in-between, which, I think, is perfect for Dragomir, becauase he tries to be a tough guy but really, he's just a big sweetie. ♥
 Ano Yume Mukou E
Niles Christian - Kugimiya Rie
Ahahahaha. Kugimiya Rie is like perfect to be Niles. She's about as girly as you can still pass off as a guy. XD But really, I think the tenderness and gentleness in her voice suits Niles well.
 Ano Hi no Gogo
Corinne Delancy - Okui Masami
Okay, so far as I know, Okui Masami is just a singer, and not a seiyuu, but her voice, I think, is perfect for Corinne, and I'm sure there's a seiyuu with a similar voice. Her voice is strong and confident, but still feminine at the same time, and that's what Corinne is all about~
 Itsuka Tenshi Ni Nareru
Viorica Hirlea - Yoshida Konami
Yoshida Konami seemed like a good choice for Viorica because she can be sort of snotty and self-righteous, but also sound very caring and kind. She could do Viorica's attitude, but also be the good sister, girlfriend, and doctor when she needs to. I can just hear her making jokes at Dragomir and Niles, or whining about Pierre. XD;
Algernon Mauvais - Saiga Mitsuki
Saiga Mitsuki has an amazing ability for creepy, making her the perfect candidate for Algernon. She has a more feminine voice when talking than when singing for some reason, which works for Algernon; it's effeminate, but not too girly so that he would loose his creepiness. Plus, the femininity would tie in with Niles' voice. <3
Perceval Rousseau - Ogata Megumi
Percy is amazing enough as it is, but with Ogata Megumi as his voice, he would simply be enough to make me melt! Ogata Megmi is the perfect choice for Percy because she can do a hard-ass bitch, I'm sure, for when he's being a General, as well as his melty around-Algernon personality (come on, she voiced Kurama, she can do anything!) She does a perfect girly-man voice, and it's just awesome X3
 Dirty Heroes
Donavan D'Aubigne - Narita Ken
The only thing I know Narita Ken for is Alesshio Yuraino from Ueki no Housoku, but I think he could be a good Donavan. He demonstrated his ability to sound snotty, which, I think, could easily transfer to Donavan's eccentric tone. He also can do angry well, and I think he could work out well when Donavan gets dangerous. Not to mention a song called Dirty Heroes is perfect for the head of the Berceuse Malheureuse ♥
 Ano Hi Kara
Faustino Esparanza - Saito Chiwa
Saito Chiwa is the perfect candidate for Faustino because she can be boyish but cute at the same time; it doesn't sound too girl, but it comes off simply cute and adorable. I think she could pull off his innocent nature pretty well, as well as how cheerful he gets when he pleases Donavan. ^^
 Sorezore no One Way
Eliana Esparanza - Tanaka Rie
Tanak Rie is perfect for Eliana because her voice is very mature and calm sounding. Though Eliana's freaking gullible, she's a very calm and well-managed person, and her voice should reflect that. Tanaka Rie also can sound sarcastic, which is good for Eliana, too. X3;
Alice Johnson - Amano Yuri
Amano Yuri is perfect for Alice because she sound really ineffectual. XD; Her voice and soft and girly to the max, which is just like Alice, but she can also sound biting and mean, for when Alice is bitching at Percy. XD;; Her voice also sound pretty young, which is good, since Alice is undercover pretending to be 18. XD;
Pierre Reinard - Paku Romi
Paku Romi is amazing. Period. XD; And she would be an awesome Pierre because she can sound really stuck on herself and mean and jerky, and would be able to pull off the snide remarks as well as when Pierre actually gets pissed and throws a hissy. XD; And I can just hear her being like "No, Tatiana needs to rest!" and being all overprotective and pushy. X3 Perfect.
Tatiana Reinard - Noto Mamiko
Noto Mamiko is the ideal voice for Tatiana because it's soft and reserved, but she can also sound annoyed and whatnot, and I think she could pull off Tatiana's hidden-Hirlea-ness. XD; She would also be excellent opposite Paku Romi in the role, because when Pierre was pushy, I can see her doing the "trying to scold him and failing" sort of thing. XD;;
If you want the CD, give me a holler :D;;