When you line up your buildings, sometimes they were not perfectly aligned across the fronts. A shop or restaurant could be set back by a foot to 3 feet to make room for outside displays or tables, or "just because". This gives a visual break up to an other wise straight line, adds places for ambushing agents or cover when under fire. Awnings can be stuck on with "blue tack" to change the appearance of any shop and their easy to throw together.
Trash cans, Streetlight poles, telephone poles, trees, letter boxes, fire hydrants etc add some more cover and help bring the street to life.
Just thought to throw this out there for you while your in the early stages of construction
