I see your background image when I view your gallery in Firefox 15.0, IE9, Safari 5.1.7, Chrome 21 and Opera 12.0.1 on my PC and see no reason why the background image should not appear on a Mac running Mountain Lion as long as Adobe Flash Player is installed and activated in the browser being used to view the gallery.
One workaround would be to make your gallery's background transparent and to display your background image using HTML and CSS instead of SimpleViewer's own Background Image functionality. In doing so, your background image would be displayed behind the gallery when it is displayed by both the Flash Player and the Mobile Player (which is used to display the gallery on mobile devices and in browsers which do not have Adobe Flash Player installed and enabled).
Remove the backgroundURL entry from your gallery's XML file and use the following as your http://roedeanstudiox.com/Collections/Fall_2012/index.html page:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>SimpleViewer Gallery</title>
<style type="text/css">
body {
background-image: url('http://roedeanstudiox.com/Collections/Fall_2012/flower_background.jpg');
background-size: cover;
}
</style>
</head>
<body>
<!--START SIMPLEVIEWER EMBED -->
<script type="text/javascript" src="svcore/js/simpleviewer.js"></script>
<script type="text/javascript">
simpleviewer.ready(function () {
simpleviewer.load('sv-container', '100%', '100%', 'transparent', true);
});
</script>
<div id="sv-container"></div>
<!--END SIMPLEVIEWER EMBED -->
</body>
</html>
Steven Speirs
SimpleViewer Support Team