You can add following to top of the htaccess file you already have
Options -Indexes
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^http://(www\.)?YOURDOMAINNAME.*$ [NC]
RewriteRule \.(gif|jpg|png)$ http://www.YOURDOMAINNAME.com [L]
Options -Indexes
will restrict directory listing
RewriteCond %{HTTP_REFERER} !^http://(www\.)?YOURDOMAINNAME.*$ [NC]
checks if the request to a file is from within script or if the request has a referrer from your domain
RewriteRule \.(gif|jpg|png)$ http://www.YOURDOMAINNAME.com [L]
will redirect to your home page, if some one tries to access the file directly. You can added file extension to this rule by separating it by pipe |
symbol, e.g. gif|jpg|png|doc|pdf