Ola Keith
Well I have to say I have thought long very long before I were going to write this answer to your work. As I kinda know I`m not going to make big friends here. But besides all the "Ooooohhh`s and Aaaaaaaahhs" I spotted some things of which I think need some major work. And I have some additions which could give some extra "Schwung" to this dio. In my eyes (and I`m talking if this was my progress showing here I would say I was somewhere between 50% and 75% of the work.) This may sound a bit harsh but this is the way I see it and I want to give some pointers of which we all can learn.
I will mix it with things I like about the dio. First of all the composition is great. All the big parts form more or less the backdrop and won`t stand in front of the important things of the story
Now one thing that really sticks out for me as a point of attention is the rubble in your dio. 1. it is not enough. The rubble doesn`t give me the idea a full story collapsed down. I`m talking here at the outside of the buildings at the inside you did a quite better job of showing the rubble. The 2nd thing I notice is that it is quite easy rubble. looks like it is mostly loose bricks. Almost like the bricks were stacked onto each other without the help of Concrete. Looks like they only have to stack up the bricks again get out the Broom and clean is the damage site. The rubble needs some big lumps of wall that simple crashed down as one piece embedded in the rubble. This almost always happens with every explosion in a building.
I have found some pictures to show what I mean.
Now the top 2 pics are French color pics from WW1 but also with modern explosions you`ll see the big lumps
Above a common sight in the middle east at the moment. A destroyed house in Ramallah Look at the diversity of the rubble.
Also the addition of a lot of wood on top of the rubble in all sorts and sizes. Also the area of Rubble seems to be very small if these buildings are hit by a grenade or multiple grenades after a heavy shelling the Rubble would be spread on a bigger area. What I also noted was the lack of rooftiles everywhere in the rubble. With the roofs of so much buildings missing you would expect there will be some rooftiles among the rubble.
In your museum you say you only need to do some windowframes but I`d say there is far more to do. The top part of it.. The so called "Bell" shaped frontpart of the house with the round window is actually the attic part. I see you made it a different color there but there is no floor in it. This would be a good place for the museum to store their stuff that is not on exhibition. Plus the roof defintely needs roof beams. Otherwise it is one of the strongest structures I know because it is held in place by it`s own weight.
Above a quite common way of roof construction
A nice addition to your diorama would be one house to still have it`s stairs. This is a part that always would be standing up (even after a nuclear explosion) due to the double triangular shape. I could not find pics but it basically is a fact that stairs stand when the rest of the building had fallen apart. Also you can add a broom cupboard under the stairs.
Then I come to the buildings. Problem with making diorama`s this big is that the level and number of detail rise with the same speed. Bigger dio = more detail to add. Of all buildings you seem to have done the most work of the interior of your museum. Nice wallpaper, Nice boarding around the lower side of the room. Etc. All the others seem to only have a floor and some windows. Add wallpapers, Wooden planking to the walls (for only the half of the room the rest wallpaper) More stuff like Paintings, Crucifixes, A musical instrument. Add more stuff like tables chairs, maybe a piano. The 2 buildings next to the tanks opposite the street of the museum are looking definately as residential buildings. Not as Commercial buildings or offices. but no sign of that is found on the remains of the levels nor in the rubble.
Also it will be really drafty in thos buildings as the only have windowframes but that is actually it. Usually when a window is added in the correct place the carpenter will make a nice finishing to it by adding planks and such so you actually have a windtight windowframe and it is actually completely surrounding the wall. This is a part I really can`t translate good. Here in Holland it is called ("Aftimmeren" basically it means finishing the job)

Above you see more or less what I`m trying to explain. Some nice crafte planks to make it (a) look good (b) keep the wind out. And this with all the windows. Also the floor in the first building at the right side of the tank (looking at it in the first pic.) What happened with the floor?? I only see the beams and some beams pressumably from the floor above sticking through it but there are no planks. Where did they go with the planks? Were they working on the floor at the time of bombing. Did they get eaten by fire? In the last case it is not evident as there are absolutely no traces of fire on non of your buildings. and Fire tends not to let dissapear wood it tends to leave a very course and easy to break black piece of coal which can sit in it`s place for years.
I love the renault car that is covered in rubble great touch.
You already mentioned street signs. I take it that with street signs you mean street name signs. But all sorts of signs like traffic signs german military signs (feldlazarett, Commandantur etc. etc.) just as well as Commercial signs (wood, enamel or painted at the wall (in case it is a French, Belgian or southern german village/city and lookign at the renault I`d say it is france. )
Ok this one is really nitpicky. Lookign at your dio one thing I see is that you used 2 types of streetlights. Unless that second one next to the museum is placed there by the museum itself it would not be of that type. The reason for this is simple. The community would have bought streetlight from one and the same type simply because it looks nicer and more uniform but also they are cheaper in bulks. Believe me when you want something special it would take months and months to discuss the point and finally when the bloody thing gets placed it already reached the cost of 40 times the streetlight. But as I say I`m being really nitpicky here.
The wall around the statue would be really suitable for a derelict German AT gun in ambush position. Also that place could have some more grass and weeds growing around the statue and along the walls. Mowing the lawn was not really a priority in those days.
I take the Jagerhof is some sort of bar. So not only Chairs need to be added but maybe a bar. Empty winebottles. Tables. Some enamel commercial signs of beverages of course.
all the other stuff you already wrote. Things like Drainpipes, Glass everywhere, Electric/telephone lines. Newspapers, Cloths, Broken bottles, Jerrycans and the thing you described as "more stuff in the street" are things you definately have to do as It will make the diorama even more interesting then it is now. Just the simple thing of adding a Red or blue bike is a little touch but which will give another point of focus. Propaganda posters are a must as they will give a hint of the time and location the dio is placed.
I love all the little PE stuff you have added to the windows and such. Those grills were often seen in those days.
Last but not least and I know you will do this in the weathering stages is give the whole thing a good layer of dust. as that is somethign you will have plenty of after a good explosion.
I like the painting of all the elements in your dio and the varietion of color is very good.
Well this might seem as a lot of things but In my opinion a dio must be quite good in detail. in that way the Historical accuracy can be a bit on the sidetrack. Everything needs to be tied together very well and everything needs to be there witha reason. So far you are really on the good track and with some addition this will be a true masterpiece. Give your viewers more to looks at and investigate.
I hope you understand my point(s)