The Penguin Band will be offering a new background when they visit for the Music Jam in July! It isn’t a custom background, but it’s worth noting that the individual band members seem to be having their design modernised. This is also consistent with the previous Music Jam sneak peek of Franky on the Cruise Ship.
It’s probably likely that DJ Maxx and Cadence will also visit for the Music Jam since they always have in the past, but that hasn’t been explicitly confirmed yet, and there aren’t details about what backgrounds they could offer if they do visit. If some news is revealed about that, I’ll be sure to let you know!