Sometimes in my own work, it's not what's missing, but what needs to be eliminated or subdued. If you'll permit me: when I look at this painting, my eyes keep wanting to look at the knobs (or whatever they're called) on the chair. They "fight" with your main focal area, your face. The chair is important to the design, but maybe it needs softening by bringing the cast shadow on the wall up behind them or some other means. Just a suggestion. Edit: yes, I get stuck with a lot of my work. I put them aside in a "work on" stack so I can look at them with a fresh eye later. Usually, I'll see what needs to be done. Hope all of this helps!