Replace AJAX Spinner with Custom Spinner

replace-ajax-spinner-with-custom-spinner.css

/* 

hourglass.gif replaces the default AJAX spinner 
http://loading.io/ <- Good place to find a new one

*/

body img.gform_ajax_spinner {
	position: fixed !important;
	z-index: 999999;
	left: 0;
	top: 0;
	right: 0;
	bottom: 0;
	display: block !important;
	overflow: hidden  !important;
	width: 100% !important;
	height: 100% !important;
	background-color: rgba(255, 255, 255); /* fall back */
	background-color: rgba(255, 255, 255, 0.7);
	background-image: url('images/hourglass.gif');  /* path to your new spinner */
	background-repeat: no-repeat;
	background-size: 194px 194px;
	background-position: center center;
}

replace-ajax-spinner-with-custom-spinner.php

<?php 

// Make sure to create a transparent images 1 x 1 and upload to themes images folder
add_filter("gform_ajax_spinner_url", "spinner_url", 10, 2);
function spinner_url($image_src, $form){
    return get_stylesheet_directory_uri() . '/images/one-pixel.png' ; // relative to you theme images folder
}