Header is too large by a good bit.
Shrink down the overall size of that file (usually the culprit is the 300dpi setting, in my experience) and the site would load a LOT faster.
Even for large headers, I shoot for about 100k max in size. I downloaded the whole site using Sitesucker, and that one file is 5.1MB in size.
Your entire site is 5.8MB in size, as a perspective.
Welcome to the world of professional web design. It's an interesting profession.
Thanks,
Regis