Bowser would wear a light blue marching hat with a horizontal red stripe as well as a Bowser emblem and Blue Feather on it, and he would have a snare drum that's red, with yellow ropes, gold trims and as well as gold stars too.

General Klump would be in his regular appearance (army helmet, ammo belt, boots) given a snare drum like Bowser's, but his is blue. And would also have the yellow ropes, gold trims and gold stars.

As for Krusha, he'd have cymbals.
Bowser © Nintendo

Krusha and General Klump © Nintendo and Nelvana

An art trade for BlueMario1016