This is great, really nice use of colours and lighting. One thing I would change is that the mouth could have bit of light in it, instead of a grayscale.
Also, if you add the the top-half of the body to the image, i think it would really cap the whole thing off.
I think if you add the top half of the t-shirt (or whatever fits right) it will make it a bit more realistic, because right now it looks a bit like a floating head.
I see what you mean about the floating head.
How would you recommend that I cut off the image. Should I feather it out like I have done above? But obviously with more of the body and t shirt showing.
What I would do is make the t-shirt go all the way to the bottom so that there is no need to akwardly feather out the image.
not really sure what is going on here, i can't give you feedback if i don't even know what the concept is.
Do you mean that I should add more of the body to finish it off?