It's very empty around the sparkled specks and you have some random effects there and the outer glow around Spiderman..eh. Just blend Spiderman and it will look nice. Make sure you re-crop your canvas size.
sorry but yeah i think about this:
some rainbow bg;
random dots/brush arround the char;
multiply outerglow and/or gradient stroke.
be advised to read tuts if this really is your first attempt.
or don't ...like me, i hate reading tuts , rarely read them only if i dont remember a particular item but know the description :3