Se t'interessa puoi ottenere il risultato che cerchi solo con i CSS:

codice:
<!doctype html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Esempio</title>
<style type="text/css">
#gallery-container {
	position: relative;
	width: 500px;
	height: auto;
	padding-top: 350px;
	padding-bottom: 15px;
	margin-left: auto;
	margin-right: auto;
	text-align: center;
	border: 1px #aaaaaa solid;
}

img.gallery-fullsize {
	position: absolute;
	top: 15px;
	left: 50px;
	display: none;
}

div.gallery-item {
	display: inline-block;
}

img.gallery-preview:hover ~ img.gallery-fullsize {
	display: block;
}
</style>
</head>

<body>
<h1>Galleria con CSS</h1>
<div id="gallery-container">
	<div class="gallery-item">
		[img]images/1s.jpg[/img]
		[img]images/1.jpg[/img]
	</div>
	<div class="gallery-item">
		[img]images/2s.jpg[/img]
		[img]images/2.jpg[/img]
	</div>
	<div class="gallery-item">
		[img]images/3s.jpg[/img]
		[img]images/3.jpg[/img]
	</div>
	<div class="gallery-item">
		[img]images/4s.jpg[/img]
		[img]images/4.jpg[/img]
	</div>
</div>
</body>
</html>