Mario Maker will include more than two graphical styles, as well as music composition
When you think about it, Mario Maker is pretty much the next evolution of Mario Paint, and arguably way more appropriate. Mario Maker will allow you to build and share 2D Mario levels, meaning you won't have to wait for Nintendo to release the next 2D Mario game, you can just make one.
When Nintendo showed off the game during its Digital Event, we got to see to distinct graphical styles for levels, the original retro Super Mario Bros. and the updated New Super Mario Bros. Website USGamer.net was able to get some information regarding Mario Maker's graphical styles talking to Takashi Tezuka, and that we can expect more than just those two.
"Obviously, there will be other graphical styles included," Tezuka said. "And nothing's been decided yet, but I'd also like to include other graphics that aren't Mario."
It's true that Nintendo has its fair share of platformers, so including themes for say Metroid, shouldn't be out of the question.
Tezuka also added that Mario Maker is heavily inspired by Mario Paint, and that it will include a music composition similar to the one in Mario Paint, so players can add their own distinct soundtracks to the game.