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.
This patch expands the timer to make it 16-bit, allowing for values as high as 65535. Not only easy to use and highly customizable, but also compatible with LM. Also comes in two versions (one for xkas, one for Asar).
Make sure to read the readme for a more in-depth explanation.