Here's a quick edit, hope you don't mind.
Adressed colors (choosing for more contrast, playing with lightness, saturation and hues between shades for each surface, for most effect). Tried to keep that desaturated look the world had during world war 2.
Added stronger defined shadows (around windows and doors), to better indicate light source and depth.
Added details, such as highlights, wall grime (maybe a bit too much), some more detail to the cracks.
Simplifed some of the shapes, such as the roof windows.
You have too many similiar shades, you should exert some palette control.
I did this in graphics gale. One of the tools i prefer there is the "color replacer", which allows you to fill an area with some color, and then go with the brush and add detail, masking with just that color (sort of same as a mask from photoshop). That's how i did some of the details, such as the wall grime (that and playing with different size brushes).
I like your piece pretty much, and with some care it would look pretty neat
Lots of detail there.
