Dear Jordu,
First of all, your quality of work is
absolutely outstanding. The realism and detail are total perfection. You are obviously a remarkably skilled individual. I joined this wonderful site in the hopes of receiving motivation, encouragement, and constructive criticism. In the spirit of that desire, I would like to share my thoughts with you, if that's okay. In my opinion, there are a few minor details in Nimoy's face that require tweaking in order for you to achieve
absolute perfection. I have attached pictures to better demonstrate what I am saying including a photoshopped version of your remarkable sculpture with the following changes. Here, in my humble opinion, are the issues to be tackled.
NOSE-His nasal labial folds are not that pronounced, the end of his nose isn't bulbous, and the bridge of his nose is narrow and slightly hooked. Also, his lower eyelid furrow is quite pronounced.
EARS- Because Nimoy's ears were glued down, they dent in slightly in the mid section.
MOUTH-His top lip is sharper and more pronounced and his philtrum (lip scoop)isn't so pronounced. His lower lip isn't as wide and is slightly more pronounced, and without such heavy down turned lines at the sides.
HAIR- His sideburns are more groomed and sharp. His eyebrows are also more groomed.
JAW- Nimoy's jaw is much narrower at the bottom.
NECK-His neck is thicker where it is joined at the jaw.

I hope you don't mind me sharing my opinion with you Jordu. Once again, you are amazingly talented which in my opinion, more than warranted the time and effort it took to share my thoughts with you.
I look forward to seeing more fantastic work from you in the future!
Take care

Paul