Hi Bill, I'm using your plugin and I'm in a situation where images description is important for the user, so I'd like to be able to see it hovering every images in the metabox.
So I've modified line 78 of your plugin file to:
echo '<img src="' . $thumbnail . '" alt="' . get_the_title() . '" title="'.get_the_content().'" /> ';
Hope to see this little addition in a future version.