The stage itself is very similar to Battlefield, having one large main platform with three smaller platforms in the air, with the middle one being higher. Unlike most Battlefield-like stages, Miiverse posts made by other users will appear in the background, "cheering" the fighters on; you can also tag a drawing you've made to a specific fighter.
The Miiverse stage was added in the 1.0.8 version update. A date for said update was never given at first like the Mewtwo Club Nintendo codes. Speculation on the stage was quiet as many people have forgotten about it. When the stage finally released, it quickly became infamous.
The fate of the Miiverse stage was recently revealed when Sakurai announced news for the Lucas DLC and new Smash 4 update which included the Miiverse stage. The Miiverse stage, Lucas, Roy, and Ryu were confirmed to be released on June 14th, 2015 the same day as the direct.
The Miiverse stage was finally released for free in the new update. The new stage is considered the most controversial and cringe-worthy stage. Many smash players have encountered drawings of things such as genitals or pornography. There have also been many off-topic drawings found as well, such as pictures of Shrek.
The support communities was created for users can go to "cheer" on their fighter by drawing pictures of them via hand written messages. However, most posts on these communities are infested with memes or genitals. You can only make drawn posts on these communities, text posts are disabled on these communities.
Below are examples of posts encountered in-game on the Miiverse Stage.