The below code snippet will change the placeholder image used when maps are set to lazy load.
add_filter('geodir_map_params','_my_lazylod_placeholder_image');
function _my_lazylod_placeholder_image($args){
if(!empty($args['lazyLoadPlaceholder'])){
$args['lazyLoadPlaceholder'] = "https://localhost.com/my-image.svg";
}
return $args;
}