I have a button that is setup to switch a body background image on mousedown. I want to be able to fade out and then fade in the next loaded image.

My code:

Code:
$('#shadows_btn').mousedown(function(){
	$("body").attr('style',"background: #d9d9d9 url('img/shadows_bg.jpg') no-repeat center 4400px;");		
});
Is there any way to do this? I wouldn't mind it if the current image disappeared by the new image would fade in. Suggestions?