What I found interesting were the free background downloads you could get. In the game download folder, PNG images show up there in relation to the background you downloaded. I haven't gotten around to testing it yet, but if the game displays that PNG image, I'm wondering if you could edit that image to display something differently behind the idol.
I wondered the exact same thing from the moment I downloaded it. And as hoped, it works. No need to edit the license files, as long as the filename stays the same the game accepts it as simple as that.
Proof:

(Sorry for the boring background)
I guess that means we'll be seeing more Takane and Hibiki in MADs soon... And it probably also means Namco isn't going to try and charge us for more backgrounds, which surprises me. If they were going to make it this simple, might as well have given us a function to import our own backgrounds in the first place...
Anyway, I love the Angelic Force costume. It's my favourite Extend costume so far. I think it looks particularly nice on Makoto, Yukiho, Azusa and Chihaya.
also the only thing that i can speculate to come out in catalog 7 that is accurate is
the next song is 'My Song'
The yukata maid was also for #7, wasn't it?