Blizzard released a new update to the PTR 3.3: The Frozen Halls.  The build 10571 added some class changes and introduced the 10-player mode achievements for the Icecrown Citadel dungeon.  The 25-player mode achievements are still missing in this build.

Fall of the Lich King (10 player) Achievements

Storming the Citadel
Defeat the first four bosses in Icecrown Citadel in 10-player mode.

  • Lord Marrowgar
  • The Deathbringer
  • Claim victory in the Gunship Battle
  • Lady Deathwhisper

The Frostwing Halls
Defeat the bosses of the Frostwing Halls in Icecrown Citadel in 10-player mode.

  • Rescue Valithiria Dreamwalker
  • Sindragosa

The Plagueworks

  • Festergut
  • Professor Putricide
  • Rotface

The Crimson Hall
Defeat the bosses of the Crimson Hall in Icecrown Citadel in 10-player mode.

  • Defeat the Blood Prince Council
  • Queen Lana’thel

The Frozen Throne
Defeat the Lich King in Icecrown Citadel in 10-player mode.

  • The Lich King

Fall of the Lich King
Defeat every boss in Icecrown Citadel in 10—player mode.

  • Storming the Citadel
  • The Frostwing Halls
  • The Crimson Hall
  • The Frozen Throne
  • The Plagueworks

It’s a Trap!
Survive the Ice Jets in Icecrown Citadel 10-player mode.

Unboned
Defeat Lord Marrowgar without anyone taking damage from Bone Cyclone in 10-player mode.

Thirty One
Defeat X of Lady Deathwhisper’s adds with her bombs and then defeat Lady Deathwhisper in 10-player mode.

I’m on a Boat
Claim victory in the Gunship Battle in which every raid member visits the enemy gunship only once in 10-player mode.

I’ve Gone and Made a Mess
Defeat the Deathbringer with fewer than X raid members suffering from Garrote in 10-player mode.

Dances with Oozes
Defeat Rotface without exploding any oozes in 10-player mode.

Once Bitten, Twice Shy
Defeat the Blood Queen while having been a vampire in 10-player mode.