Custom background for menu

I have an image that I would like to use as background for menu. I can add the image to the menu, but it only fills the menu bar width and height. I want to use the full image and place the menu on a specific area of the image so that it dynamically stays in place as the image resizes. Is this possible?

Hi
this is not a problem from the menu
you shall better put the image in your template area and load the module in this area according to your image. This is a problem of design not related to the menu features
CEd