A WebmasterWorld thread asks if there are any issues with using hotlink protection for your images and the same images suffering in image search. Hotlink protection, if you do not know what it is, is when you want to dissuade others from pulling your images directly from your server. You can use hotlink protection, such as with htaccess, to either block or serve up a different image, to those pulling the images from you. But does this affect your search rankings in image search engines like Google image search?
Most of the folks in the forum discussion say there is no issue with Google and hotlink protection. Some recommend that you allow certain domains to display the images properly, such as your own domain (duh) and the shopping search engines (if that applies), news engines (if that applies), blog engines, image search engines and so on. But that list can get long.
Forum discussion at WebmasterWorld.