So, this is from the official website. Is it possible that they're actually building up to a Superman reveal? Part of me doesn't really want them to spoil his return, so I'd be equally ecstatic with a poster, featuring a new Superman picture.
Edit: Some links found in the page's source. No spoilers of any kind. Let's see what Saturday is going to bring now..
https://www.unitetheleague.com/join/...n_superman.jpg
https://www.unitetheleague.com/join/...e_superman.png
https://www.unitetheleague.com/join/...sm_468x468.jpg