Hi,
if you don’t need the header part, just the top-nav menu then I have a workaround for your problem, as you can see on my site:
Dubai Programok
You should change the header height to a thin line or even nothing and voilá you can save the shadow effect over the background image
I put the following into my custom CSS for this to achieve:
#header .header-inner {
float: left;
transparent: true;
padding: 0;
width: 100%;
background-color: transparent;
clear: both;
height: 2px;
}
Best regards