For what it's worth, this leak has moved all three mii characters to their own spot to the left of K Rool, and with whatever the Chorus Kids seem to be doing, they could be what has been scaring Wario this whole time.
Still, I'm extremely hesitant to accept this leak because it's promising Shadow and Ken as echoes, but then Banjo, Geno, Isaac, Chorus Kids, possibly Mach Rider and Kos-Mos for base, which is way more newcomers than expected at this point.
Also, I'm not sure but have we ever had a picture of this battlefield without any characters on the poster? This tweet has a picture that shows the mural artwork without any characters and I want to check -
https://twitter.com/trzef/status/1054995203600326656