Interesting shot. I think a brighter background would've helped. Also, a little more detail in the building and cropping out the bottom half of the image would have added more impact.
I think some added contrast to totally remove the detail in the building, and to brighten up the sky a little, would help improve this shot. I would like to see a closer crop too, to put more emphasis on the photographers. As it is, there's a lot of wasted space in my opinion.