RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://www.domain.com [NC]
RewriteCond %{HTTP_REFERER} !^http://domain.com [NC]
RewriteRule .*\.(gif|GIF|jpg|JPG|mpg|MPG|Mpeg|mpeg|MPEG|rm|RM| avi|AVI)$
http://www.domain.com [R,L]