With a table:
<table height="400">
<tbody>
<tr>
<td valign="middle"><img /></td>
</tr>
</tbody>
</table>
The 400 is just something I picked. You will need to define a height on table so it is taller than your image.
A jquery solution would be good if you wanted to try and use divs and junk, but if you don't care you don't care. You also have to rely on JS being turned on.
HTML:
<div id="imgContainer" style="position:relative;">
<img style="position:absolute;" />
</div>
JS:
$('#imgContainer > img').each(function(){
//get img dimensions
var h = $(this).height();
var w = $(this).width();
//get div dimensions
var div_h =$('#imgContainer').height();
var div_w =$('#imgContainer').width();
//set img position
this.style.top = Math.round((div_h - h) / 2) + 'px';
this.style.left = '50%';
this.style.marginLeft = Math.round(w/2) + 'px';
});