Okay, starting with the characters and stages...

CHARACTERS*
Raiden (based on the opening)
Shao Kahn (based on the opening)
Sub-Zero
Scorpion (naturally)
Reptile
Kung Lao
Mileena
Sektor
Johnny Cage
Nightwolf
Kitana (based on earlier news)
Sonya (based on earlier news)

*Now, someone had posted a list of Voice Actors a while ago but I couldn't find it. I'm trying to think of the clues that were mentioned, but the only ones I can remember are Jax, Jade, Cyrax or Smoke, and Shang Tsung.

That's 16/17 characters right there...

ARENAS
Shao Kahn's Arena
Living Forest
Dead Pool
The Pit
Shang Tsung's Throne Room
And what looks like a Rooftop in a ruined city

FATALITIES
Kung Lao slides his victim down the middle of his hat
And the Pit spikes are back