I like the use of the smooth purple for shading and the primary light source being that of a dull orange/brown, it works. The only suggestion I have is bring the lightest green colour down slightly to match the smoothness of the overall piece. 

 I prefer the original to the edit, though there are probably a few places where pixels could be shifted so things are less jaggy, particularly along the bottom left of the face where the yellow highlight is.

looks great though, lovely palette.

 haha, i wonder why that might be? maybe the colors contrast weirdly at actual size, but it matters less when it's large?

either way, i reuploaded with a 400% enlarged version next to the original.

Interesting. When you zoom in this pixel looks so beautiful!!! It's still pretty good when not zoomed in, but wow I really like it zoomed in...

 thanks for the draw over! i see what you mean about clarifying the pixel clusters, it looks cleaner that way.

i'm accustomed to acrylic and digital painting, and i think i went into this pixel portrait thinking in terms of brush strokes and opacity when i should've been thinking about clean shapes and how to best use a limited palette.

ah well, just need more practice. :)

thanks for the feedback, everyone.

I personally think this is fantastic as it is.

I really like this piece! I think that at that size, you have to be a lot cleaner in putting down pixel clusters, may it be in their size and shape.

So here's an edit I did:
I hope it helps! :)

Yep, portraits are hard to do, but you did very well. :) The colours are playing together quite nicely and the proportions look believable.

You may want to add some AA on the cheak/neck and refine some of the pixel clusters.

Good one! :)