Twenty Twelve Changing Header Image and Link

Hi, I’m using the Twenty Twelve theme for https://www.boozefinds.com. I’d like to use the randomization feature for header images, but in addition to toggling through images, I’d like each image to have a different link. In essence to showcase difference site sponsors. I think I found out how to expand the image size to 100%, but would that also center the image on the site? Thanks!