I'm not too experienced with anatomy either, but without knowing the gender of the character and the pose you're going for, here's a few things I can offer:
-The right forearm is too short and the hand on the end is small.
-The knees are lower than they should be.
-Your character has no heels on his/her feet.
-The hood on the shirt is a bit small. It doesn't look like it would fit over your character's head.
Those are a few suggestions that come to mind immediately. Again, I could offer a bit more if I knew more of what you were going for. I'm fairly sure that there's at least one comprehensive anatomy thread around somewhere, but I can't find it right now. Maybe someone else can point you in the right direction. Although I'd have to agree with the people above that you should start smaller. I know that you want to produce something big before the motivation disappears, but the motivation always returns eventually, and if you get some other sort of practice in, you be better prepared for this when the urge returns.
Then again, that's just my two cents. I have to admit that in all of the time I've done pixel art, I don't think I've actually tried to do a single image that big before.