Well looks like it’s been already changed 🙂 but If you want that image to scale based on the size of the browser window. Here is the tip, try this CSS
#pref-navbox {
background-image:url('https://demo15.thewritedesigner.com/wp-content/uploads/2014/12/art-deco-nav-03.png') no-repeat;
background-repeat:no-repeat;
background-size:contain;
background-position:center;
}
Do not set width, height, or margins.