Do not edit the Twenty Eleven theme. It is the default WordPress 3.2 theme and having access to an unedited version of the theme is vital when dealing with a range of site issues. Create a child theme for your changes. Once your child theme is active, we should be able to help with the customisation.
Thats fine, I’m just curious about the changes.
I’ll set the child theme up later.
You can try experimenting with applying the image to the menu div. Something like:
.menu-main-menu-container {
background-image: url ('images/yourbg.jpg');
}
You could also try playing with the other background attributes to get it displaying how you want it.
http://www.w3schools.com/cssref/pr_background-position.asp
Note: untested.
re: image map – you could add one somewhere in the header.php file if you really wanted one.