This goes beyond your C&C request but all crit is helpful, learn to love it. The pose is a bit awkward. It's as if you were shot at random, with no thought to yer poise for the portrait; you're slouched up against your closet door jam for some reason.
Akira is referring to starting out more sketchy, massing in the basic shapes with some thought to volume and space, so ponder light as you sketch out roughs and try and throw in some light and shadow.
Final lineart should always be preceded by exploratory sketches. Forget it's pixel art for a moment.
Another thought, if you're experimenting around, is to just trace directly over your portrait reference shot there, scaled down as desired. Assuming you have a layered graphics program handy.