I think the map looks great as is, but I agree with both poster above. The streets could use a bit of "dirtiness" to them and the roofs could use a bit more definition. My suggestion would be to simply add a dust layer on top of the streets that you draw into with subtle strokes, particularly in the center of the streets where most people walk. Also, you could add a bevel-emboss effect on the rooftops. The current look has a rather "flat" feel to it. I'm not at all familiar with City Designer Pro, so I'm not sure if that is an option, but my first suggestion definitely is.