Change the background bodyjpg image

Hi,
I want to change the background image (body.jpg) in traveller theme and I am using the free version of this theme. I tried to change the image by replacing the image with another image which has the same resolution, changing the path of the image and editing the style.css. Background image doesn't change. I love this theme and hope to purchase. I would really appreciate any help regarding this.

html {
	background:#111;
}
body {	
	color:#111;
	font-size:13px;
	font-family: 'Arial', sans-serif;
	position:relative;
	background:url(images/AT-body.jpg) no-repeat top center ;
}

Cheers,
Sameera

Hi!
Could you give us the URL of your website, please.