Super Mario Maker 2 Won't Feature Costumes
Super Mario Maker 2 will not have costumes, according to a recent video from GameXplain. In the original Super Mario Maker, one of the graphical styles allowed you to use costumes to replace Mario with another character effectively. This then allowed people to create custom levels, suited specifically to that character. It was all strictly aesthetic, but that is exactly the type of thing people loved about the first game.
The feature has been dropped, along with amiibo support, to focus more on the four characters that will all be playable in Super Mario Maker 2. While there is always the potential for the feature to return in the future, I wouldn't get your hopes up. While have four playable characters will certainly be nice for people who love to build themed levels, the community will definitely miss out on costumes.
It's a shame to see a beloved feature being dropped, even with all the new features that are coming to the game. Super Mario Make 2 will once again allow you to build your own Mario levels, and the set of features for the building seems to be very robust. Players will once again be able to share their levels with people all over the world using Switch Online.