A loose paint that is sensitive to pressure and friction is used to paint the dance floor. It slowly wears off as people dance on it. Underneath there's a nice picture that is being slowly uncovered.
Fun and aesthetics.
Seeing that there's a constructive "job" being done makes dancing even more enjoyable.
A way of visualizing how much people actually trample on the dancefloor and which parts of it are being trampled on more.
There could be different formulations of the paint depending on how quickly one wants it to wear off. It could last a month or so until the picture is revealed, but it might as well be made just to last one night, during a single dance party. Each party could have a different picture hidden under the paint, the picture could represent the theme of the night, or (in cases where paint is made to hold longer) - a theme of the month or a year, etc.
The problem with the paint that wears off very quickly (during a single night) is that the "recycled" paint will then be everywhere - on people's shoes, debris of it lying on the ground, etc. You'd then perhaps need a brush to sweep it off for the picture to be clearly visible.
To simplify the process of changing the images underneath the paint, large stickers could be used. That way you wouldn't need to use two layers of paint. The staff would stick the image to the floor, then paint the special paint on it and when the paint wears off, tear it off and stick another one. The smooth surface of the sticker might also help the paint to wear off.
When the paint would start to wear off and the dancers would begin to see parts of the image, they might intentionally gather to the places that still need trampling on to reveal the rest of it, this would be a kind of puzzle-dancing.