Feel free to start a thread nominating actors for any of the following roles:
[Let me know if I forgot about anyone]
Frame Story:
Arwen
Celeborn*
Galadriel*
Eirien - Arwen's friend
Celebrían (in flashback only)
Elladan and Elrohir (appeared in Season 1 frame also but were not yet cast)
*Also appear in Main Story
Main
EVIL characters:
Thuringwethil (Episodes 3-6) - female - possible bat shape, possibly still a bit more human-form
Drauglin (Episodes 5 and 6) - male - werewolf form is more wolf and no humanoid version. [voice]
Tevildo (Episode 4, possibly other episodes) - male - cat-like (think black panther or saber-toothed tiger, not kitty cat) [voice]
The oldest generation of elves:
Morwë (Avari) [Episodes 2-3] - 1/2 of the 'Noldor' stayed with him at Cuivienen
Nurwen (Avari) [Episodes 1-3]- 1/3 of the 'Teleri' stayed with her at Cuivienen
Ingwë (Vanyar) [Episodes 1-8, 12, 13]
Iminyë (Vanyar) [Episodes 5-8, 12, 13] - minor character, probably does not need to be cast
Finwë (Noldor) [Episodes 1-13]
Míriel (Noldor) [Episodes 1-6]
Tatië (Avari) [Episodes 2-3]
Mahtan (Noldor) [Episodes 4-10, 12, 13]
Elwë (Teleri-Sindar) [Episodes 1-6]
Olwë (Teleri-Falmari) [Episodes 3-6, maybe several later ones as well.]
Círdan (Teleri-Falathrim) [Episodes 3-5]
Lenwë (Teleri-Nandor) [Episodes 3-4]
Beleg (Teleri-Sindar) - [Episodes 4-6]
Mablung (Teleri-Sindar) - [Episodes 4-6]
Eöl (Avari) - [Episode 1 and 3]
Rúmil (Noldor) - [Episode 7 and ???]
Next Generation:
Indis (Vanyar) [Episodes 2-13] - daughter of Ingwë and Iminyë
Fëanor (Noldor) [Episodes 6-13] - son of Finwë and Míriel (note: child actor needed in Episode 6]
Fingolfin (Noldor) [Episodes 7-10, 12, 13] - son of Finwë and Indis (note: child actor needed in Episode 7)
Finarfin (Noldor) [Episodes 7-10, 12, 13] - son of Finwë and Indis
Findis (Noldor) [Episodes 7, 9, 10, 12, 13] - daughter of Finwë and Indis (note: child actor needed in Episode 7), minor role
Irime (Noldor) [Episodes 7, 9, 10, 12, 13] - daughter of Finwë and Indis who will die in the Kinslaying
Nerdanel (Noldor) [Episodes 7-13] - daughter of Mahtan, wife of Fëanor
Anairë (Noldor) - [Episodes 8-10, 12, 13] wife of Fingolfin
Eärwen (Teleri-Falmari) [Episodes 8-10, 12, 13] - daughter of Olwë, wife of Finarfin
Miscellaneous:
Ents! Treebeard and his wife Fimbrethil, as well as possibly the other two 'old' ents (Leaflock and Skinbark) will appear in episode 4 with the Nandor and will need voices
Arien (Maia) - we did not cast her in Season 1, apparently
Radagast (Maia) - he has a minor role in Episode 2, so casting him at this time is optional
Tom Bombadil (???) - he has a cameo each season (Episode 4 of Season 2, he sits by a river)