hello, Robertgiffin, you painting is beautifull, and if i could, I only would like to tell you that you can give you portrait alive, giving some brilliant points in the eye, adding a lacrymal gland in the left corner. May be, if you give an impresion of transparency for the glass, you'll have an other result.
Dont worry, it's only my point of view. Look at a Raytracing production to see what you can obtain.
experience comes from bad judgements, good judgements come from experience (old wise indian proverb)