The alley walls are too washed out, and the archway is terribly blown out. The photographer, bride and wedding party marching off is a cute idea but this environment just lacks character.
I think this would have worked better had the assistant actually been the subject and been facing the camera. There is too much tunnel with the action being so far away it is hard to tell what is going on.
The composition of this shot is good... I can see why you found it a good opportunity for this challenge... I admire your courage in shooting one of the most difficult (IMHO) photos to expose correctly - you exposed for the darker interior and that made the lighter parts blow out - I like the textures in the ground and the wall. The right side should be cropped tighter.