You could try:
$("ul.gallery-large li").hover(
function () {
$(this).find('img').addClass("hover")
.animate({width: '200px'}, 200);
}, function () {
$(this).find('img').removeClass("hover")
.animate({width: '100px'}, 400);
}
);
and CSS:
ul.gallery-large li img{height:auto}
Here it is working: http://jsfiddle.net/dxFq6/1/