Richter will do his iconic peace sign from Castlevania: Rondo of Blood.
In competitive play
To be added
Jack's line "Begone! You don't belong in this world, monster!" in the Vampire Killer trailer is a direct reference to his famous line from Symphony of the Night, "Die, monster! You don't belong in this world!" The line itself is from from the original PlayStation version's English dub, spoken toward Dracula in the game's opening, and is famous for being one example of the original game's poor but nonetheless fondly remembered English voice acting.
Jack's red palette swap seems to be a reference to the nameless, red-clad rival vampire hunter from a cancelled Sega 32X Castlevania game, commonly referred to by fans as Castlevania: The Bloodletting.