I don't know how close you are to calling this one "finished," and you may have already had this in mind...
but I would suggest adding a few things to give the scene a bit more realism. I'd add a street sign or two (maybe "No Parking," maybe a light pole on the "corner" with street names, that sort of thing. I'd also add a fire hydrant, and dirty things up a bit. The "concrete" under the buildings is much too clean and pristine. I'd also add some "litter" here and there, maybe a trash can... those kinds of "little things" that make a diorama look much more like a real street scene and give the diorama "life."
Also... if the buildings are not solidly attached to the base, I'd move them much closer together. Most of the time buildings of this era were built very close together, with only a very narrow walkway between them, many times adjoining buildings are even touching.