A graphical hack of M2, replacing everything in the game with Mario themed stuff, Samus, the walls, the enemies, everything

It's called Marioroid: Marimus Returns, a sequel to Marioroid on NES.

"The princess has been kidnapped, but she is not in another castle, but on another planet!
Bowser has kidnapped the princess (again!) and taken her to the alien planet SR388, where he has made it his base. Control Marimus to search the planet’s cave system and kill all the Koopas as you try to rescue the princess. The bizarre gravity of SR388 means that you don’t have the necessary force to stomp on enemies, so you will have to shoot them with your new gun. Find new abilities, such as the Tanooki Suit, P-Wing and Bombs to explore new areas and kill every Koopa on the planet!"

Included in the zip is the IPS file, a few screenshots and a boxart image I made

If you want to play with colour, I suggest this palette:
#ff5500 for light grey and #6d2400 for dark grey on backgrounds
#ffaa7f for light grey and #6b0000 for dark grey on sprites