Interesting problem.
I have a few ideas.
You can turn "show images" off in your browser. Are you getting images on other sites? I assume so, but if not, check that browser setting.
Now, in your admin site, do a right click on one of the places where an image should be displayed and select "properties." Note the location of the image file, and then confirm using your FTP tool whether that image is indeed in place.
Another idea ... install another administrative template. It will come with its own set of icons, etc.
I like the one from joomlaworks.gr titled "Minted 1.5" and install it on all of my sites. (It works fine in Joomla 1.13 sites).
You can download that here:
http://www.joomlaworks.gr/#downloads_section. You would install that using Installerers -> Templates Admin. And after installing, be sure to make it the "default" admin template.
Those are just a few ideas that come to mind.