I love everything about this piece, the composition and the theme and the colors are amazing If you want to add more volume to the face I think it will look even better. I think keeping everything but the face volume less will make it look a bit like Klimt and I just love his style If you were to add shadows to the face I suggest you use warmer tones with blue shadows only here and there, otherwise I think the piece will lose the balance I indicated some shadows, hope this helps!

Hello there! The illustration itself looks really good! I like the colour palette and painting style. However, if you're adding cast shadows in areas such as the neck and a bit of the nose, I think it would be ideal to add shadows to other areas as well, such as the side of the head, the hair, the eye area, etc. This will help give the portrait more volume. Keep the direction of the light in mind. I think the light is coming from the right side based on the shadow on the neck, although the shadow on the nose suggests the opposite... Choose a light direction and make sure the cast shadows follow it. Hope this helps!