farei semplicemente una cosa del genere
codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<title>rounded border for images with css3 + jquery</title>
<style type="text/css">
body {
	background-color:#ccc;
}
.roundedCorners{
	border:0;
	border-radius:20px;
	-moz-border-radius:20px;
	-webkit-border-radius:20px;
}
</style>
<script type="text/JavaScript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>

<script type="text/JavaScript">
/*<![CDATA[*/
$(document).ready(function(){
	function supportBorderRadius() {
		var div=$('<div>');
		var bRad=['borderRadius','MozBorderRadius','WebkitBorderRadius'];
		for(var k=0;k<3;++k){
			if(typeof div.css(bRad[k])!=='undefined') return true
		}
		return false;
	}

	if(supportBorderRadius()){
		$('img.rounded').each(function(){
			var div=$('<div class="roundedCorners"></div>');
			div.css({
				'width':$(this).width(),
				'height':$(this).height(),
				'backgroundImage':'url('+$(this).attr('src')+')'
			});
			$(this).css('opacity',0).wrap(div);
		})
	}

});
/*]]>*/
</script>
</head>
<body>

</body>
</html>
chi supporta css3 vede arrotondato, gli altri i soliti angoli

ciao