Super Smash Brothers - In the original CSS, the potraits are 44 x 40. He cut 4 pixels of each portrait's widths so they're 40 x 40. Now there's room for 6 more characters.

(HE)^6

With this fact now known to me, I'm going to say we're getting our hands on the TwIndies (Shantae and Shovel Knight), the Predators (K. Rool and Wolf), Inkling and a random other character we don't know about quite yet.