google images ignoring disallow

[apollo]

I have this text in the robots.txt file:

*******************************
User-Agent: Googlebot-Image
Disallow: /
*******************************

This is the only example I could find on the net regarding disallowing google images. In validation it gives this warning:

********************************
1 warning Field names of robots.txt maybe case insensitive, but do capitalize field names to account for challenged robots. (eg: User-agent)
User-Agent: Googlebot-Image
******************************

My images are now appearing in google image search. Is my robots.txt syntax correct?

When I set up this file google was the only engine crawling images but now there are plenty but I still only ban google. Is there anyway to ban all image crawlers?

Here is my full robots.txt:

User-Agent: Googlebot-Image
Disallow: /

User-Agent: ia_archiver
Disallow: /

Thanks

[pixel_juice]

The validation error isn't very clear, but you need to use a lower case 'a' in User-agent I think ;)