Fix for http://drupal.org/node/69453 Thanks Tobias

gmap_location.module

@@ -538,6 +538,7 @@ function theme_acidfree_gmapnodelabel($n) {
 function theme_image_gmapnodelabel($n) {
   $out = '<a href="'.url('node/'.$n->nid).'">'.check_plain($n->title).'</a> <br>';
   $out .= image_display($n,'thumbnail');
+  return $out;
 }
 function theme_gmapnodelabel($n) {
           // Allow a module (where the module name matches the node type name)