Not a bad hack, but I still have some notable highlights. Some palettes [like the ones in the chocolate level] aren't good, and you should keep a consistent color style by playing with a few of them, but not oversaturate too much. You can also keep a cape in one level throughout the others (can't remember which), so you should prevent that by applying this patch.
And the very last level is kinda repetitive, what with the overuse of the same setups of shell jumps over and over, but at least the Bowser fight was kinda challenging but still messy on the difficulty curve due to how Bowser tends to bounce.
Overall, it's acceptable, but be sure to update it in the future!