This is a bug we have identified in Design Extender, we will be releasing an update early next week, this issue should be included in that update.
in the mean time, the fix is to edit the map JS file in the webassist/google_javascript folder.
do a search for :
'google_javascript/images/
and replace each instance with:
'webassist/google_javascript/images/
to update the marker image paths top the correct location.