Hotlink Protection will prevent hotlinking of your images while keeping them visible to feed readers.

How it works:

• Referrer check if someone requests an image from your blog.
  If the referrer is not empty and not your blog the request is redirected to an information image
• The image urls in the feed are replaced by an alternate url. This url is not protected by a referrer check so online feedreaders get the image

more info and download....

Hotlink Protection, WordPress, Plugins, WordPress Plugin