I think you're on the right track with the face. The most glaring issue that stands out the most is the pupils/iris, they should be bigger. Also if you flip the image I think you'll see how lopsided the head looks because of the hair.
There's also another issue here I think and that's how far the shading under the cheek bones is being pushed. With the light already striking the cheekbones above it already suggests there is some sort of elevation going on there -having the shadow under them makes it look like there's a cave or something there.
I also think you should be more frugal with that highlight, if you use it in more select places, and in smaller quantities (like one or two pixel clusters) you'll be able to make certain aspects of the face stand out a lot more -like where the highlight on the nose is, is perfect but having it on the chin and the cheekbones sort gives it a puffy look.
I don't know if you've thought about it this way, but since it's pixelart and you're working at this res you have to think about suggesting features with light, rather than copying the face 1x1. I think for the sake of learning you should cut down on some of your darker colours too so you can concentrate on other things! You don't need too if you're comfortable right now, but yea, really on the right track with this!