it have on Photoshop, not sure about GIMP.
Edit>Transform>Wrap
some guide lines will appear, me the center smaller, fixing the size of both sides at the same proportion
So I don't think the thing you should worry about is the color of the eyes, I think your focus should be on either re-doing the whole color/shading process or scrap it and go with the head above.
no variation of line weights, blunt pencil
hands look like claws
the girl looks ok, fat chin is the main issue
the clothing folds are nice, but anatomy go
the girl, was drawn with a blunt pencil in places, didnt sharpen the pencil often enough, really thick lines
and generally you use quite thick outlines on all your works