gistfile1.php

<?php
add_filter( 'gform_ajax_spinner_url', 'tgm_io_custom_gforms_spinner' );
/**
 * Changes the default Gravity Forms AJAX spinner.
 *
 * @since 1.0.0
 *
 * @param string $src  The default spinner URL.
 * @return string $src The new spinner URL.
 */
function tgm_io_custom_gforms_spinner( $src ) {

    return get_stylesheet_directory_uri() . '/images/loading.gif';
    
}