Probably the best way to do it would be to find or create an image larger than today's current screen size. Then put it in a div as the background. Put your menu image in the div over it. Something like...
Code:
<div id="page" style="background: url(4.jpg) no-repeat;height:120px;width:100%;text-align:center;vertical-align:bottom;overflow:hidden;">
<img src="menu.png">
</div>
That would show part of the background like in sample1.jpg. And more of the background like in sample2.jpg.