Your decor could be poster sized playing cards on the wall, black and white checkerboard table cloth, and pink plastic flamingo's as table decorations. You could have the student council dress as Alice, the Mad Hatter or the Queen. Guests could dress in Victorian best. Signs are written so the words are flipped backwards. The icing is inside the cake, not outside.
Streamers are on the floor.
Paste balloons on the stage upside down, with their strings attached to the ceiling. Tablecloths are under the table. Girls ask boys to dance. Brave guys wear dresses. On the wall, there is a mural showing dogs walking their people and prisoners arresting their jailors.