You need to add a markers URL parameter. Like this:
http://maps.googleapis.com/maps/api/staticmap?sensor=false&markers=size:mid%7C40.737102,-73.990318|40.755823,-73.986397&size=600x600&zoom=12&path=color:0x0000ff|weight:5|40.737102,-73.990318|40.749825,-73.987963|40.752946,-73.987384|40.755823,-73.986397