Are you setting this up on a or the Dolphin emulator ?
Disclaimer: Modifying your Wii console involves risk. Ensure your console is not powered off during the installation process to avoid "bricking" (rendering the console useless).
For specialized, heavily modified versions of the game (like New Super Mario Bros. Wii - The Next Levels or SNES Edition ), custom WADs are used to create distinct channels that look different from the official game.