I noticed one teensy, l'il thing with The Djoke's serve...
When the sprite begins to take the racquet down and back to start his motion, there's this weird sort of super hyper-extended
elbow thing going on where his forearm and upper arm bend backward in a rather un-natural almost painful
sort of motion...(sorry..only constructive
Maybe in a future update you might be able to tune or "straighten" this part of his arm...
Other than that, it is awesome!
Also, perhaps in the future it might be nice to mimic some of the "pre-service" characteristics, such as how certain players bounce the ball...because often it's also a very personal and identifiable feature of their style...for instance, Djokovic bends a bit more at the waist and is very deliberate with his bounce (only no need to bounce it 20 or 30 times