You did a great job getting the shapes and form down accurately.
8 colors are not terribly easy to work with, but it looks like you worked them in there well.
I have very little advice to offer except possibly the glasses. I'm a bit biased against 'cross hair' glasses shape, which really don't seem to reflect their form in the photo. I tried out a quick edit mostly shows on the glasses and face:
The trade off is that the glasses look a little less transparent. I ended up trying out two glasses and necks, but that becoming a judgment call.
I also messed around with the hand and jacket a bit, but I'm even less sure about them.
Wish I could help more. Keep up the good work.