The header image is 500px high? That's... excessive. In comparison, this image here is 512px high;
http://icons.iconarchive.com/icons/t.../Crab-icon.png That image is almost completely filling my browser window, I would highly not recommend making your header and menu buttons more then 200px, 250px tops - they are great in theory, but a person can go through hundreds of page reloads every single time they're on one site - you want to see content, not the header image.