Nintendo surprise-dropped a brand new stage for Super Smash Bros. Ultimate, and it's a mini version of the classic Battlefield stage. Small Battlefield - or "Smol Battlefield" as the internet prefers - is included with update 8.1.0, which is available for download now.
The new stage accompanies the normal-sized Battlefield and Big Battlefield, offering a close-quartered ground for more intense brawls. Though, I checked out the stage myself and it doesn't seem much smaller than the standard Battlefield, but it is missing the middle platform that's suspended in the air. Competitive Smash Bros. players can select Small Battlefield as a Preferred Rule in online matches.
Update 8.1.0 also adds the ability to pick stage-specific music for the Battlefield, Small Battlefield, Big Battlefield, and Final Destination stages. Further, the threshold for qualifying for Elite Smash has been broadened to allow for more players. Nintendo says they're continuing to look into Online mode and to expect further updates in the future.
In addition to those more specific changes, the new update comes with a host of general fixes to improve gameplay, but Nintendo didn't give specifics. No balancing updates were revealed in the patch notes, so don't worry about your main being nerfed this time around.
Usually new Smash Bros. Ultimate stages receive the proper launch treatment in a paid DLC pack alongside a new character, like with Min-Min and the Spring Stadium stage. You won't hear any complaints from me though - a new stage is a new stage, even if it is just a smol version of an old stage.
If you're just starting out or haven't completed your roster just yet, here's how to unlock every Smash Bros. Ultimate character.