Did you look at the CSS in the sticky footer? Pinning a panel so that it does NOT scroll out of sight - #7 by stucork
From my inexpert CSS view of things, it looks like the important bits are:
position: fixed;
left: 0;
bottom: 0;
You could work those into an Anvil role and apply it to your image and see what happens. The fixed
positioning should be relative to the window.