we have a few images currently being indexed by google and we want to remove them from the index. We have removed the .aspx page which linked to the image (but the image still physically exists on disk at the same location), so will google now automatcally update its records, to not show our image? Or do I need to delete the image aswell? thanks!
The most complete way is to prevent images being accessed by sites other than your sites domain. Many isp's offer an option to disable hotlinking, apache can be configured to do it or you can use htaccess.
htaccess
RewriteEngine On
RewriteCond %{HTTP_REFERER} !^http://(.+\.)?yourdomainname\.com/ [NC]
RewriteCond %{HTTP_REFERER} !^$
RewriteRule .*\.(gif|bmp|png|jpe?g)$ /path/to/image/hotlink.gif [R=301,L]
Alternativly you can write the last line using the forbiden flag
RewriteRule .*\.(gif|bmp|png|jpe?g)$ - [F]
I'm not sure, but i think you might have to block it manually
http://www.google.com/support/webmasters/bin/answer.py?answer=35308