Since all of the other PlayStation All Stars leaks have proven to be true (including the game’s development), it would seem reasonable that an image dump of stages and characters would turn out to be accurate. Still, take it as face value.
Characters include Dante, Cole McGrath, Spike (Ape Escape), Jak (but no Daxter?), Nairoko, Ratchet (but no Clank?), Raiden (Metal Gear), Sackboy, Sir Daniel Fortesque (MediEvil), Heiachi, and Toro from the PlayStation marketing side in Japan.
What’s disappointing is the lack of historical perspective. The oldest characters here without recent activity is Fortesque, but this leaves out early icons like Jumping Flash or a character from Battle Arena Toshinden. One thing Nintendo does remarkably well is include characters no matter their obscurity, go so far as to include slivers of history like Mr. Game & Watch in Smash Bros. Sony isn’t that friendly with their history apparently.