Nice rendering, and great job getting down the essence of the portrait. I would just recommend brightening up the area of his face that falls into the light, as not only does it add clarity, but it reinforces the composition of lights vs shadow from the original image. It helps to squint at an image to notice the shapes of light vs dark, as these are key guides when approaching a painting. Keeping the same strength and direction of light on his face also supports the believability of the lighting set-up, as it falls from above and hits his surrounding costume in the same manner. Hope this helps! :)