I am coding a new project just for hobby (http://www.mundopano.com) since I want to add a way for people to embed the pano to any blog or whatsoever, I needed a way to make sure nobody could steal my images (or at least make it as hard as possible for them).
If you want go into the website and load any pano, then try to get the image, even using firebug.
of course the Cache is always there and it is possible to get the image from the cache, so this is not a 100% protection, but it will make it hard for anyone to steal them
it's a PHP/MySQL/.httaccess solution, I can post the complete code is someone is interested
I will explain how it works
The idea is to use session variables and stream the image with another file that calls the mysql table that has all of your pano file names, then destroy the session right after streaming the image, if they try to load the image without the session being loaded then they will get an error :)