No, once you get to the final cutscene, that's it. There's no more content beyond that.
Viewing post in Slick as the Devil jam comments
Must be a tiny little bug then: after I beat the game, i tried playing again, but after the intro cutscene, the sign said IIIII I (6 I's) and the gameplay was basically the final round. I thought it was gonna be extra hard levels for beating the first five rounds without items. My mind would have been blown!