Ok so seeing your head, there's room for improvement, take these tips with a grain of salt.

So first, are you using a template? If not I'll provide you with a template, simply open it with your image editing software of your choice, and make a layer over it.
*note* this image is 1024x512, this method you don't have to predict the flat to sphere compensation. if you rather draw in 512x512 or whichever your item resolution is
(of course drawing in 512x512 and using a 128x128 the item will resize to fit the lower resolution) If you want the 512x512 template feel free to ask for it, I can provide it.



-------------------------------------------------------------------------

Ok so seeing your head it seems a bit stretched onto the sphere. I can help you with a few pointers on better mapping.
So firstly as you can see the green circle is generally where your face should be,
As you can see in the image I color coded parts where you can map a face
Firstly, the green, it's "best" to simply draw within the circle, you can adjust this but this is a general ballpark of where the head would look best.
The blue is generally where the eyes should be on that horizontal mid line, you can go over or under to fit your preference of course.
Lastly the pink is generally where the mouth best fits, same as the eyes, you can go lower or higher to fit your needs.



-------------------------------------------------------------------------

Here's an image of how this flat looks ingame, as you can see it's not exactly stretched out and the face sits more centered.



Happy texturing!