Ok, so if it is all of those images, how do you know fixing the background image worked? To call images in the stylesheet, you need to put them in the skin1/images directory and call them like this:
background: url(images/imagename.jpg);
To call images in the templates, you use:
<img src="{$ImagesDir}/imagename.jpg">
If you do that, they won't give you that warning. If they do, something is either incorrect with your http/https setup, or you have an absolute path called somewhere.