These new details and screenshots come from Nintencast.
Mario Kart Wii is set to release April 25th. View 17 Screenshots

-New track D.K's Snowboard Cross (a giant half-pipe that is perfect for stunts).

-Miis will be spectators in the background.

-Coconuts Mall has players driving around a huge mall, with multiple routes.

-While racing online, the players names will be displayed above there characters.

-Koopa Trooper is a playable character.