I feel the character is pretty well done. "Cute" haha.
The background just doesn't have that feel. I think even a black background with small stars would be a better choice.
If you were to keep the background the same way, I feel it needs a bit of work at the top,, and maybe a darker shade of grey which slowly gets lighter?
The platforms seem like their just pasted onto their, maybe help attach the one to the ground like its in the ground, and for the ones in the air, they feel like they were perfectly sliced and propped into the air..