Hello Dave
Here is another example, since the first example was not clear enough.
What I mean, the textures of dead material is excellent in your illustrations.
But living material requires a different approach. I hope that this new example, gives more insight into what I mean. I hope my comments do not bother, I'm just trying to help.
I can not guarantee that this portrait seems real, but there is no reverence material that can be a good example.
Regards,
Martin