That’s really difficult to say. I mean from an objective standpoint, jaw, cheaks, neck and the back of the head have more detail in the original image so if you 'd want a 1:1 replica, you might want to work on that.
But I think your main focus right now shouldt be proportions and also finding a diffrent own take on the sculpt. Your Proportions are already good, but the original has a lot more “flow” to it and looks more handmade and dynamic (basically it emulates a more dynamic lineart-style)
Regarding the own spin: I don’t know. Make it a Pirate, give it a Hat, give it ridiculus renissance style makeup, make it a Robot. Possibilities are endless.