How to set width and height in jQuery

I have a background image and I am trying to optimize the site by specifying height and width for all images. I cannot figure out how to set width to 450 and height to 350.

<!-- BACKGROUND IMAGE -->
    <script src="js/supersized.3.2.1.min.js"></script>
    <script type="text/javascript">
jQuery(function($){
$.supersized({slides:[{image:"/images/heritage/background.jpg"}]});});
    </script>