I meant that if you wanted a more antique feel (and what you did does the job well enough in my opinion), I guess the only solution would be to use the technique of ole. Taking your quill (kidding, take your slightly rugged brush) and tracing an insane amount of parallel lines to emulate shadow.

You can (barely) see what I mean on the image below :
Capture d’écran 2017-02-02 à 00.06.05.png

I really do not think you need to do it, let me be clear, I'm just saying that you did such a good job that the only solution I find to get a more realistic feel is to go native