Still needs work.
Let's see. You do need BG and FX in this piece I mean come on it's the Mario Theme! I could give you advice, but I'd rather you listen to it. Go to the Audio Portal, go down to the bottom where the search bar is. Change it from Author to Details and type in Acid Plumber (Mario ReMix) and listen to that one.
I think you could have potential. Now then if you're going for a piano classical thing with Mario then search the Audio Portal change it to Author and look for Gwave and listen to the Super Mario Bros. theme their.
That's all I have to say.