This plugin works perfectly on the front end, and mostly on the back end as well. The only issue I have is when I am on the page edit screen, and I choose an image for the header from your meta box, the image that should show up below the selection is always a broken image. It shows up fine on the front end. It just doesn't within the admin edit screen itself. The url to the broken image seems to be missing the image name, so it's just pointing to the header-images folder, but there's no filename after that directory in the url.
It's not strictly necessary, I suppose, but it would be nice if my client could actually see what they chose before publishing a page.