There's a lot to like about this. However, some parts look very clean to me (the green pipe, the boxes, the coins, Mario, the ground, the icons on the bottom) and other parts look a bit more noisy (green dithering, dotted clouds, turtle shells). I think I would prefer one or the other, personally. Still, good job! 
It's been a while since I've logged into my profile here in PJ. Thank you very much for the feedback. I'm planning to make another mockup o/