You had said that the scale was going to be 53 pixels per mile...roughly 1 pixel per 100 feet. At that scale most buildings would not be seen and large buildings would only be a few pixels at most and certainly you could not put in roads. I would suggest increasing that scale so that you can fit in more detail. However, if you're not going for total accuracy then the topography can be one scale and you could do the city at a different scale. It looks a little cartoony or video-gamey but I've done it recently...I say scale shmale. Another option is to do the city as an inset map (in a corner or something) and do whatever scale you want there.