<IfModule mod_rewrite.c>

RewriteEngine On
RewriteBase /wp-content/uploads/

RewriteCond %{HTTP_REFERER} !^$ [NC]
RewriteCond %{HTTP_REFERER} !photozero.net [NC]
RewriteCond %{HTTP_REFERER} !zhuaxia.com [NC]
RewriteCond %{HTTP_REFERER} !xianguo.com [NC]
RewriteCond %{HTTP_REFERER} !google.com [NC]
RewriteCond %{HTTP_REFERER} !feedburner.com [NC]
RewriteCond %{HTTP_REFERER} !feedsky.com [NC]

RewriteRule .*\.(gif|jpg|png)$ unavailable.png [L]

</IfModule>