In DLC:
Blue Falcon (F-Zero)
F-Zero Course (Pic 1)
Animal Crossing Course
Weird Playground looking Course (Pic 2)
Forest Course?
Pic 2 is based off Excite Bike
DLC Pack 1(November 2014)
Link, Tanooki Mario, Cat Peach
Blue Falcon, ?, ?, ?
Wario's Goldmine, F-Zero Course, Excite Bike Course, ?, ?, ?, ?, ?
DLC Pack 2(May 2015)
Villager(From Animal Crossing), Isabelle(Animal Crossing), Dry Bowser
?, ?, ?, ?
Animal Crossing Course, Forest Course(MK Arcade GP DK Jungle?), ?, ?, ?, ?, ?, ?
There.
I'm still saving for a Wii U, hopefully should have one mid- September with this game.
Personally, they should add Bowser Jr. back in the game and maybe Funky Kong too. Nintendo has just given us the 4th Mario and 4th Peach in this game... Hoping for more retro tracks though!
And DLC means Downloadable Content