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.
As the name implies, this is a pure vanilla hack - it contains absolutely no custom stuff (aside from custom levels, of course.) No custom palettes, no mixed tilesets, not even tiles placed through Direct Map16 Access, just pure level design.
Because of that, it's possible to port the whole hack over to SMA2, which is what I did. The file "PureVanillaHack_SMA2" should obviously be patched to a clean SMA2 ROM.