At the moment I'm using

<Files image?.jpg>
order deny,allow
deny from 209.185
deny from 209.85.238
deny from 66.249.79
deny from 72.14.199
deny from 8.6.48
deny from etc. etc. full list of all googlebot IP's
</Files>
But there must be a better or easier way to say "for any user agent with google in it block access to image1.jpg,image2.jpg,image3.jpg". A way that I can then later add new user agents to, and that doesn't require knowing all search engine IP's

Can anyone help?