Looking good so far...some suggestions below:
If you are going to use outlines I'd consider using it all over, for instance all around the hair. It is up to you personally what you want to do but it is usually good to have the outline style consistent all over.
On the bottom row, with the third image, the right eye needs to match the left. I appreciate you tried to make it that way because the face is at a 3 quarter angle, but you can't leave the white center/pupil of the eye exposed or it will look strange. You could even copy the iris of the left eye and paste it on top of the right one. (From this point you may or may not want to slightly edit it so it isn't absolutely identical, but whether this matters is up to you, I think it is probably fine).
I also think the tuft of hair on the right side could be shorter (like 3 pixels shorter) because of the perspective you have going.
If you are going to use outlines I'd consider using it all over, for instance all around the hair. It is up to you personally what you want to do but it is usually good to have the outline style consistent all over.
On the bottom row, with the third image, the right eye needs to match the left. I appreciate you tried to make it that way because the face is at a 3 quarter angle, but you can't leave the white center/pupil of the eye exposed or it will look strange. You could even copy the iris of the left eye and paste it on top of the right one. (From this point you may or may not want to slightly edit it so it isn't absolutely identical, but whether this matters is up to you, I think it is probably fine).
I also think the tuft of hair on the right side could be shorter (like 3 pixels shorter) because of the perspective you have going.