Can't change the map marker icon

I can confirm this. maybe an issue with a newer wordpress version and usage of the old media uploader dialog. the javascript returns “undefined” for the image source.

you may work around this by filtering the option value until fixed by the plugin author:

function my_filter_wpsl_map_pin( $option )
{
    	$option = '/path/to/image.png';
	return $option;
}
add_filter( 'option_wpsl_map_pin', 'my_filter_wpsl_map_pin' );