Add the following to the .htaccess file:
# Rewrite Rule for images
RewriteCond %{HTTP_REFERER} <URL of page accessing your domain>
RewriteRule ^(.*)$ <A HREF="http://<same" TARGET=_blank>http://<same</A> as above URL>
You would replace the <URL of page accessing your domain> above with the domain name
and path of the page that is referring to your domain. For example:
www.their-isp.net/users/mypage/
The RewriteCond directive states that if the {HTTP_REFERER} matches the URL that
follows, then use the RewriteRule directive. The RewriteRule directive will redirect any
reference back to the referring web page.
Hope this works havn't tried it myself.