RewriteEngine On
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !aroche\.net [NC]
RewriteCond %{HTTP_REFERER} !aroche\.org [NC]
RewriteCond %{HTTP_REFERER} !jaroche\.wordpress\.com [NC]
RewriteCond %{HTTP_REFERER} !images\.google\. [NC]
RewriteCond %{HTTP_REFERER} !google\. [NC] 
RewriteCond %{HTTP_REFERER} !ubuntu\.chapinware\.com [NC]

RewriteRule \.(jpe?g|gif|bmp|png)$ - [F]