<div class="fade">
<img src="1.jpg" />
</div>

.fade
{
background-image:url('images/2.jpg');
width:300px;
height:225px;
}

$(document).ready(function () {
$(".fade").hover(function () {
$(this).find("img").stop(true, true).animate({ opacity: 0 }, 500);
}, function () {
$(this).find("img").stop(true, true).animate({ opacity: 1 }, 500);
});
});

<div class="fade"><img src="1.jpg" /></div>
<style type="text/css">
.fade
{
background-image:url('2.jpg');
width:300px;
height:225px;
margin:0 auto 15px;
}</style>
<script type="text/javascript">
$(document).ready(function () {
$(".fade").hover(function () {
$(this).find("img").stop(true, true).animate({ opacity: 0 }, 500);
}, function () {
$(this).find("img").stop(true, true).animate({ opacity: 1 }, 500);
});
});
</script>