Full Width Header, 1000px body

[Seven Skins]

You can do something like this but your site will not display nicely on mobile devices.

#header .site-logo {
	min-width:800px;
	max-width:8000px;
}
#header .site-logo img {
	height: 100px;
	width:800px;
	max-width:800px;
}