Well, Alex; if you're doing this one just for fun, then I hope it turns out how you want it!
Generally, a true "diorama" tells a story, and that story should be evident to the viewer. If you were to build this as a serious dio, as opposed to a more "diplay"-type of base, you should keep in mind that rarely would you see a line of vehicles parading closely together down a street in actual combat conditions in an offensive role--unless it was like a full-on retreat down a narrow corridor. Just something to keep in mind.
Also, be aware that streets in Europe look a LOT different than in America--especially in the 40's! Asphalt and sidewalks would definitely NOT have been the norm--more like cobblestones or even dirt.
Your base there as you are portraying it would be more suitable for modern armor; otherwise it's going to look like you have German panzers parading down Mulberry Ave in California...
P.S.--also, are you using Photobucket? If so, could you downsize your photos a little when you load them in? They're SO huge when you blow them up that it's very difficult to see anything on the screen because the pictures are just so big. You can choose the size you want to load them as when you upload them from your computer This would really help us here who are trying to view and comment on them. Thanks!