Your map looks like it's really coming along. Screenies are getting prettier, and asthetics seem to be shaping up all-around. It seems like you are really trying to figure this thing out, therefore, I thought I'd give you some advice that has helped me tremendously in creating maps (and more).
The big problem I'm seeing here is a lack of compelling composition. This composition - the broad strokes of your shapes is the foundation of your map. Understanding this stuff is essential to any artist, as it applies to anything that humans look at. I work with some great artists, and just recently (within the past couple of years) had a very 'AHAH!' moment while studying the beautiful pictures and environments they create. It's a very simple principle, and once you realise what's going on, you will see it everywhere. Our world is a visual rollercoaster - a never ending wave of stacked objects that kind of piramid up and down all around us. Pay attention to where your eye goes as you walk down the street... along the sidewalk, to a gutter, up to a room, to an antenna, back down to a window, down an archway, back to the street. This is the organic way in which our eyes move across the landscape be it a room, or a mountainscape - we are constanly riding along the contours of objects around us pulled from one shape to the nest. These contours, the shapes which define the objects only exist because there is contrast. So... when creating an image, you want to take advantage of this knowledge, and create shapes (using contrast) which pull the eye around the image in a satsfying and organic way. There really is a science to this stuff, and when once you start to see it, you realize that it's not that hard to use. So anyway, enough rambling. What I've done is tried to illustrate these concepts with a few quick paintovers of your images. Hopefully you see what I'm getting at with these - they are only meant to illustrate the point of composition, not specific things you should change.
- I really like the feeling of this building on the right, but it's bordering on repetitious, and this view is begging for some more interesting shapes. Use the skyline as much as possible, It's basically a big flat color waiting for you to stack interesting shapes against it. the red line is the path which you eye takes - the rollercoaster.

The second shot has a ton of potential, but also suffers from too much repitition and a fairly dull skyline...your eye needs more action.
Last shot...I really like this busted building, but think you should play it up some more. Take advantage of the theme, make it more dramatic.
Hope this helps. I know that it helps me to do these kinds of exercises with my own maps. Drawing over screenshots is a very powerful tool that all mappers should at least try. It could save you a lot of time when trying to figure things out.
Duncan