Tip: You can use Lunar Magic's Overworld Layer 3 Editing system to edit or create your own layer 3 images (castle bricks, fish, rocks) and apply unique effects per level via the Layer 3 Bypass in the main editor.
Finally, I can submit a hack longer than one level! This is a hack I made.
Luigi has fallen down another pipe, and found himself on another island. He noticed it was considerably larger than the last one he was on, and he also saw a desert in the far distance. He got out his binoculars, and saw Bowser... on top of a castle, roaring with triumph as he had captured Mario! Luigi decided to embark on a quest around the island to save his brother!