https://github.com/neteye/jquery-plugins/tree/master/activity-indicator

<script type="text/javascript" src="js/jquery.activity-indicator-1.0.0.js"></script>

// 読込時に実行
$(document).ready(function(){
		$('body').activity({
		outside: true, align: 'center', valign: 'center'
	});
});

// 読み込み完了時に実行
$(function () {
	$('body').activity(false);
});