The writers' of Shaun Of The Dead are in this film as a cameo, they are the zombies that the people have their picture taken (around the time when Riley is in the gambling pit run by the midget).
Tom Savini plays the "machete zombie." This is a callback to the original "Dawn of the Dead" where he played the living version of that character- a motorcycle riding hillbilly. He also did makeup effects on Dawn and Day of the Dead.
George A. Romero actually has his own little trademark in his zombie flicks. It's a zombie on fire. In all his zombie movies of his there is at least one who ends up completely engulfed in flame.