Hey, Martin!—Welcome to the Forum! Glad you joined us and I think you will find a lot of great input from the other professional designers who frequent these pages.
Getting to your questions, the shadows in the background do not look like doctors—they look more like KKK members on holiday, or Death Watch characters from the Dark Ages. I think a bit of (darkened) doctor garb in blue or gray, maybe stethoscopes too?
As far as the colors, the “nuances” are definitely lacking. Depending on how the image is to be printed, it may lose the effect I think you were shooting for. Speaking of shooting, the basketball backboard and net are not telling the story. Both it and the “doctors” need more definition. Remember, design is always about communication. If the image does not communicate, it needs adjustment.
One more thing—his left arm looks like he’s been fitted with a bionic arm instead of a temporary brace. Take the metal look out of it, and clean-up the black marks on the ball, so it communicates that it is indeed, a basketball.
I hope some of these suggestions help, but remember, I am only one voice on this forum and others may have better ideas for you. I wish you the best of success for this project!