1: Muddy textures, it looks like you used bumps rather than normal maps on the stones of the column, and building. While bumps are fine for that kind of thing, it looks like you have the distortion WAY too high which is leading to what appears to be a sloppy job. If you are trying for low resolution geometry that is fine, however, in order to ‘up the ante’ you may consider using a wider range of textures and upping the resolution of the image, not the geometry.
With the high levels of detail in the foliage it just puts the viewer off when they look at the lower detail buildings.
2: The ‘pings’ on the light shade look a bit on the harsh side. This one also suffers from a lack of detailed textures, particularly on the buildings. One suggestion I would have would be to pick a texture size and work with it. I’m not sure if these are rendered out of your modeling software or an actual game engine. You can download UDK for free, learn that and pull your renders, you can use some of the tools in there to dynamically update textures to get the feeling you are looking for. Ultimately the strengths here are the lighting, but it falls apart on the texture work.
3: This one suffers from many of the issues cited in the prior pieces. I’d recommend updating the geometry and placing it a bit higher res. Unless your looking at putting a title on a portable device such as a droid or ipad. Even then, you can up the resolution quite a bit and the texture detail to get a more ‘realistic’ image.
4: Again, this one seems to be disconnected from the rest of what’s going on. It appears as if the building in the center is of much HIGHER quality than the rest of the scene. This creates a disjointed sense in the viewer. Consider upping the quality and detail in the buildings that are moving forward. Some depth of field to fade the lower resolution buildings in the background may improve the overall drama of the scene.
Hope that’s what you were looking for. At the end of the day, I would spend quite a bit more time working through these images, levels, and models to up the quality, and depth of the images.