HeroClix Minatures
I suggest you consider getting some Heroclix figures by Wiz Kids. They are pre-painted figures on 1.5 inch bases. Although there are lots of superheros, they have gang members, policemen, scientists, Master Mind Henchmen and the like. Go to the Wiz Kid site and find what guys you want. Then go to ebay and find the ones you want for few bucks. Usually the 'commoners' you would want go pretty cheap. If nothing else they make nice NPC's.
If you do not like the bases, you can snap off their bases and then glue them onto inch squares. Just put them in the freezer for a half hour and then the glue will become brittle enough for you to snap the figure off the base.