Hi Pete,
My first reaction is...Awesome:-)
After reading the post I understand you want me to really look closley and see what could be improved (if anything). So,
I put my nose into the computer screen and start picking it apart (*S*) Now, I myself only use black/white and metalic acrylic colors so I'm not that familiar of how the other colors "react" with leather.
All the greens, I like that it is not consistent, just like mother nature, at the same time it could need some more darker greens (like shaddows) in some places...corners. I'm kind'a amazed that the acryllic came out so nice as it did.
All in all, this is one of the best pieces I have seen with acryllic paint ever, you should be proud of it, I REALLY like it, it's most beautiful:-)