Show clrcle overlay instead of marker in google map?
The view settings should allow you to choose the marker style. Don't have the module installed to check but a comment on the "Provide Gmap marker field for use in Views listing" feature request illustrates how I remember it: 


  Under style: GMap in your view try clicking on the setting icon next
  to where it says GMap. An option box should appear below the view with
  some options:
  
  
  Marker handling: By content type (for node views)
  By term (for node views) 
  Use single marker type