This leak only brings chaos and nothing more... and if it's fake (it most likely is) the thing that they are fooling most of us is just annoying.
The fact is that the background is different, and there is solid proof of that.
It's possible that it has been modified on purpose to make it seem like a fake, in that case it's not unlikely that some of the characters in the banner are fake too and not all of them are in/someone has been removed from the picture in the edit.
So, even if the leak is real, it's probably not the real roster, not completely.
If the background is different because it's fake, then it's fake ad we are all losing our time.
I think this is the most likely option, though I don't exclude the other one.
The 4chan post with the same characters as the leak means nothing, because it's very possible that the post and the leak are made by the same person/group of people and they specifically posted the list of characters on 4chan only to support the leak and make it more credible. The fact that it has been posted close enough to the banner leak, is an hint that the two things are connected and that the leak may be fake. If that roster was real, it would have probably appeared more often in text leaks, assuming that a small percentage of them have actual legit informations. All the text leaks so far, despite using the same names over and over, have all been very different each other, in a way or another, by mentioning different third party reps, and different amounts of characters.
I think they have posted the list of characters close to the leak so that people would assume that there wasn't enough time to create the picture based on the text leak in such a short time (I don't know precisely how much time it was, but I have read somewhere it was close), and to make it seem like both the text leak and the banner leak were unrelated and both legit (so basically, a move to support the leak's credibility), but ironically, I think that it would have been more credible if it was based on a text leak (or better, on several text leaks) of many weeks ago, in that case there would have been the doubt that maybe between all the fake leaks there were some overlooked real ones (kinda like the "there is a true image leak between the fakes that has been overlooked" of some days ago).
Anyway, I'd be ok with that roster if it's real. It would annoy me a bit that there are the Chorus Kids instead of Karate Joe, but still, the other characters are all characters I'm neutral to, and I like Geno.
It's just that this roster is missing a surprise character... I don't know, it's kind of disappointing that every character in the picture is someone that's already been speculated (and fake-leaked) countless times, between Ultimate and Smash 4's speculation cycle... and honestly this is another thing that points toward it being fake, it really seems a fan's wishlist and I have an hard time trying to think that this list is actually official.