Not bad considering the size of it, however...

...Rather than just outlining the title, try to AA it instead. It just looks bad.
(use the grey you have and the darkest blues)
Crotch is all so wrong, that's a girl's package you got there ;)

Not clear it but make it 'bulge' out since its a dude.

Don't bulge it tooo much though. That's just what Jalonso wants you to do. 

  You need to learn about anti-aliasing and fundamentally human anatomy and the structure of folds.
  Why are you doing a pixel art poster so large? To me it seems to be that you've decided you're making a poster with pixel art techniques, but because the poster will be big you decided that you needed to pixel in a large scale too.
  I disagree.
  If you're going to do it in pixel art, i would strongly suggest making this more clear and more the central idea of the poster. To do this you should make the poster design in much smaller dimensions then have it scaled (although so that the pixels stay clear) to fit the poster when it's printed.

That's just my opinion though. Good luck :)

You also want to avoid using a lot of dithering styles of shading on skin. Cell shading works best with skin. Also consider your hues. You want a more skin-like tone, not yellow.