This was probably achieved by taking the fighters from the existing banner and pasting them on to the leak, in which case it doesn't say anything about 'moving' the fighters. I believe the original poster noted that almost every fighter had to be manipulated in some way.
Still, with a blank Battlefield the leaker could potentially use that same "pasting" technique.
Yes but thats extremely time consuming and tedious task, As a digital artist, let me try to EXPLAIN is possible but would requires days even weeks of work:
-Even if you had the blank canvas, you would basically had to crop EVERY single character from the illustration that has them all. Or you would need access to the layered PSD file, of the ORIGINAL illustration and this is extremely unlikely since it would require the original artist/artists sharing the original file so would be almost impossible.
-Then clean those crops since the original illustration is extra busy and cluttered, we are talking of hours or even days of work (assuming you are a professional or a very good amateur). We are talking of 70 crops, 70 cleanups.
-At this rate we would have need about 3 MAJOR LAYERS/folders in photoshop: The blank battlefield, a carpet with ALL the 70 crops of the characters and another layer in between that needs to be created just for shadows.
-Then, positioning in a very meticulous way every single crop and adjusting the shadows accordingly, this would need a eagle eye precision and working with the original image side by side.
-You would need to prepare the render/illustrations of the newcomers in a way they have the same or a very similar artstyle to that one of smash (even tho is very tiny and pixelated so this could be kinda easy).
-Afterwards, youll require to position the renders/mockups/illustrations of the newcomers in a way they feel interactive with the rest of the roster, adjust their positioning and do final retouches to the file.
-Then printing this file in such a way that it makes sense as a decorative banner for the round adornments.
The staggering amount of work required to do that just to troll the internet, would be borderline maniac ( wouldnt be surprised tbh).