I think robots.txt changes won't be enough, so would I have to use htaccess? What would be the string to use and also how to remove images already indexed in Google Images? Thanks guys
Copy and paste the following into the robots.txt file in the root (main directory) of your Web server: User-agent: Googlebot-Image Disallow: / User-agent: Googlebot Disallow: /*.gif$ Disallow: /*.jpg$ Disallow: /*.jpeg$ Disallow: /*.png$ Code (markup): These changes should be sufficient to block Google from indexing any of your websites images. To remove already existing images you can resubmit your website to Google's Index. Go to Webmaster Tools and use the "Fetch as Googlebot" feature to force a re-indexing. When you enter a url here it give you an option to "Submit URL to Index". You can also remove particular images by using the "Remove URL" feature in Google Webmaster Tools. Check https://support.google.com/webmasters/answer/1663419 for more details
Actually after this month has passed it didn't work. The robots.txt didn't change anything (and google crawled it) and Fetch as Googlebot is for pages rather than linking up to block images. Any other suggestions? Thanks guys