Вариант ...
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8" />
<style type="text/css">
.effect{
display: block;
}
img{
display: none;
}
</style>
<script src="http://code.jquery.com/jquery-latest.js"></script>
<script>
$(function(){
$('#panel nav a').hover(function(){
$('img',this).toggleClass('effect')
});
});
</script>
</head>
<body>
<div id="panel">
<nav>
<a href="1.html">Чебурашка<img src="http://javascript.ru/forum/images/smilies/dance3.gif" alt=""></a>
<br><a href="2.html">Гена<img src="http://javascript.ru/forum/images/smilies/victory.gif" alt=""></a>
</nav>
</div>
</body>
</html>