Ok the first thing is the size of the diamonds on the shoulders of the shank, There is only space for 3 there, and although you added extras to give it a shiny effect, it starts to look unrealistic. [link] The type of setting you are trying to create is this. It is called a pave' setting and if you look closely you will notice that the stones are held in with tiny beads that are created from the material of the ring. the other thing is the size of the claws holding the central stone (claws like that would not be able to hold a stone that size). I feel that they should be thicken in order to get a more realistic look. But that's just my opinion. Next the central stone has too much shine and busy reflections which seem to give it a strange look, and shape? Not sure how you would go about rectifying it?
Apart from those small thing I really like this! Very well done!