Here's some early footage showing character design and some animation of specific characters (included in review copies of the Batman Year One DVD).

Excerpt from official press release:

Justice League: Doom finds Superman, Wonder Woman, Flash, Green Lantern, Martian Manhunter, Cyborg and Batman on their heels when a team of super villains discover and implement the Dark Knight's "contingency plans" for stopping any rogue Justice League member. The story is inspired by Mark Waid's much-heralded "JLA: Tower of Babel."

[Nathan] Fillion, the star of ABC's hit TV drama Castle, made his debut as Green Lantern/Hal Jordan in the recent Green Lantern: Emerald Knights. Fillion made his initial DCU bow as the voice of Steve Trevor in the 2008 hit Wonder Woman.

Currently headlining the cast of ABC's popular Private Practice, Daly originated the title character's voice in the landmark cartoon, Superman: The Animated Series. He has reprised the role in two DCU films: the 2009 extravaganza Superman/Batman: Public Enemies and the 2010 thriller Superman/Batman: Apocalypse.

In addition to current primetime stars Fillion and Daly, the cast is a grand reunion of the original group of actors who provided the voices of the Justice League for the cartoon of the same name and its follow-up, Justice League Unlimited. Reprising their roles are Kevin Conroy (Batman: The Animated Series) as Batman, Michael Rosenbaum (Smallville, Breaking In) as Flash, Susan Eisenberg (Superman/Batman: Apocalypse) as Wonder Woman and Carl Lumbly (Alias) as J'onn J'onzz/Martian Manhunter. Bumper Robinson (A Different World, Transformers: Animated) joins the cast as Cyborg.

The Justice League faces two sets of villainous teams in the film – The Royal Flush Gang and a sextet of notable evildoers. The latter group includes three voice acting alumni of the Justice League animated series: Phil Morris (Smallville, Seinfeld) as Vandal Savage, Olivia d'Abo (The Wonder Years) as Star Sapphire, and Alexis Denisof (Angel) as Mirror Master. Also opposing our heroes are Carlos Alazraqui (Reno 911) as Bane, Paul Blackthorne (The Dresden Files) as Metallo, and Claudia Black (Farscape, Stargate SG-1) as Cheetah.

Superman in Justice League: Doom

Justice League: Doom will be a loose adaptation of the Mark Waid series, "JLA: Tower of Babel". The movie was adapted and written by Dwayne McDuffie right before his death in February 2011, and is directed by Lauren Montgomery.

The film will feature Tim Daly, Kevin Conroy, Susan Eisenberg, Nathan Fillion, Michael Rosenbaum, Carl Lumbly, Phil Morris, Olivia d'Abo, Alexis Denisof, and David Kaufman reprising their roles of Superman, Batman, Wonder Woman, Hal Jordan / Green Lantern, Wally West / The Flash, Martian Manhunter, Vandal Savage, Star Sapphire, Mirror Master, and Jimmy Olsen from Batman: The Animated Series, Superman: The Animated Series, Justice League, Justice League Unlimited and Green Lantern: Emerald Knights respectively. The film will also feature the voice talents of Bumper Robinson as Cyborg, Carlos Alazraqui as Bane, Paul Blackthorne as Metallo, and Claudia Black as Cheetah.

(via wikipedia)

The line-up is impressive, Batman vs. Bane, Flash vs Mirror Master, Wonder Woman vs. Cheetah, Green Lantern Vs. Star Sapphire, Martian Manhunter vs ? In addition, the feature will include Vandal Savage, the Royal Flush Gang and more.

The Flash Vs. Mirror Master

Bonus, official Batman: Year One trailer

Warner Home Video will premiere the Justice League: Doom trailer during its presentation at New York Comic Con on Friday, October 14 from 3:00-4:00 p.m. in the IGN Theater. Justice League: Doom will be released on DVD, Blu-ray and instant video early next year.

Upcoming DC Animated features are Superman Versus The Elite and The Dark Knight Returns.