It seems to me it might be best to create icon_0 and icon_1 and then perform the substitution where it is referenced as we iterate over the recordset. I.e:
var marker_0_<?php echo $Google_recordset_id; ?> = new GMarker(point, icon_0);
I am thinking that using a different icon will require different shadow attributes, etc hence the need for a full second icon definition.
Or, am I over-complicating things?