How do I get Ultimate Branding to use the https protocol for images?

When I use an image from my media library as my login image, the image is pulled from the location using the http protocol not the https protocol on my https site, causing a message to appear in some browsers that the login page may have corrupt content. I've noticed that images are a major cause of this security warning in the https protocol, and that changing the hardlink of the photo to a https address solves the problem, but have been unable to figure out how to get ultimate branding to use https addresses -- it keeps defaulting to http...