Marble Madness
Fortunately for modders, Marble Madness is featured in the unofficial FinalAlert and FinalSun map editors, and works the same way as it would have in the original editor.
How Marble Madness Works
How Marble Madness functions is very simple: when enabled, it replaces a tileset with another, as specified by the MarbleMadness flag. Both sets should have similarly shaped tiles and the same amount of tiles for optimal results. However, this effect is purely visual, and the tile information isn't actually modified in IsoMapPack. Once the mode is turned off, the editor returns to displaying the original tile graphics.
Trivia
Marble Madness mode is named after Marble Madness, an arcade video game published in 1984, which involved controlling a marble in a colorful, isometric 3D environment not unlike its namesake map editing mode in C&C games.