Hi! I think you already got a decent idea of how to draw crystal arms just need to consider form more when rendering the arms. Try to draw arms in base dark color to get the form right first (see A) - I would highly suggest looking up references of violin players for anatomy. Once you got the form, start adding rough detail of single stones covering it while considering the light source. Add highlights to the edges of those stones to imitate shiny crystal texture. Try to avoid white color and reserve it for finishing touches. I made lighting magic? more blueish so it doesn't look so lifeless. It also makes it easier to tell which light is reflected from the arms. Don't forget to add light from the magic to the clothes and violin as well. I did a bit of paintover to give a general idea - obviously can't paint it all in a short time. Hope it helps a bit.
Thank you so much for your feedback and a great paintover! It helped immensely!
Np!