Capcom has confirmed that Rachel, who appeared in the 3DS version of Resident Evil: Revelations, will be a playable character along with Hunk in Raid Mode. In addition, there will be two new enemies: the Wall Blister, and a "surprise new creature."
The company has also revealed some details about Wii U exclusive features. Here's an excerpt from the press release:
Wii U players will be able to take advantage of the unique features of that system with three different styles of play. Using the screen on the GamePad players can quickly access their map and weapons, or switch the GamePad out for a Wii U pro controller. Alternatively, players are able to transfer all the horror to the GamePad as the title utilizes Off TV play.Source: Capcom via Go Nintendo
The Miiverse feature will offer Wii U players further exclusives. Players can post a dying message on the Game Over screen for other players around the world to see. The ‘Creatures Voice’ function allows players to personalize the thoughts of enemies in Raid Mode to taunt their friends. Screens of all the Wii U functions can be downloaded here.