Google will now be alerting webmasters if there is a manual action taken against their website because of “image mismatch” issues. Google explains this notification on their help archives. The page states the following.
If you see this message on the Manual Actions page, it means that some of your site’s images may be displaying differently on Google’s search results pages than they are when viewed on your site.
No worries though. To get such a notice you would have to intentionally manipulate your website’s images to try and provide different images to Google’s image search results when compared to what people see on your website itself.