It should be cropped toward the right of the window so that the shadow of the branch perfectly balances the window. I feel there is too much space on the right and the eye flits back and forth. As Mayfair 710 wrote, it is the simplicity of this photograph which gives the image its impact. And although I am strictly a B/W believer, this photograph, I think, can only work with the color you have in it. It is a fine photograph as it is. And, in my opinion, cropping as I have suggested shall make this a real stunner.
I thing john is right about the right side. the shadow on the lower right and left work together and the heavier shadow on the upper left balances the window. but I feel the same slightly on the right and some on the top would make the photograph much easier to look at.