Dr. Cendrillon Studying

This is my Original Character, Dr. Cendrillon (whom I don't have a first name for yet, still...) and he's studying his plants. This is the first time in a loooooong time that I made a digital picture with a background. I would like some constructive criticism, please (I don't have a premium membership yet, though.) I used Paint Tool Sai and spent a few days (on and off) on this.