You can't make images stretch with CSS, and as far as I know, image maps are not stretchable by any means.
What you need to do is separate your header into two or more pieces and attach them as background images to different elements in the header, like #logoWrapper and #logo, one anchored to one side and the other anchored to the other side. Then when the page stretches, one part will slide under the other at the seam. Google "sliding door method" for the standard tutorial.
This requires designing your header to allow the sliding without covering/cutting important parts.





