At Hollywood Arts, it's a tradition to decorate your own locker on both inside and outside as you can see them in almost every episode. If they graduate Hollywood Arts, they have to clean up their lockers.
Tori: "Make It Shine" quotes with a dark blue skyline background that lights up. She also has pictures of Katy Perry inside. In a recent Drive By Acting Exercise video, we can see a poster titled "Who's Hot?" with Dan Schneider's picture above it. However in one scene in Crazy Ponnie instead of saying "Make It Shine", it said "Make It Rot".
Jade: Black with scissors glued on. Next to Robbie's locker.
Sinjin: Light blue with regurgitated food pieces that were never digested stuck on with an industrial adheisive.
Robbie: Red with a mosaic of baby bottle nipples from his childhood. Inside there is a picture of a cat. It is slightly smaller than all the other lockers since the bottom is Rex's separate locker (how this was accomplished is unknown). He stated in Tori & Jade's Play Date that he keeps rubber gloves and sponges in there also.
André: A working keyboard that he must play a certain arrangement of notes to unlock and lock. Diagonally above Beck's locker.
Cat: Pink with a piece of red flower on the middle of the locker.