If you are looking to get your images ranked in Google, John Mueller recently made a comment regarding indexing images that SEOs should take note of, that could impact sites relying on traffic from image search.

In the last Google Webmaster Office Hours, someone asked about images being crawled when switching to a CDN or changing the URL in some way, such as moving images to a subdomain.

Since images tend to be crawled a lot less frequently, it can take a bit of time for that to actually happen.  So that’s one thing with images that is a bit different than with web content in that we crawl images a lot less frequently than web content.

This is probably something many don’t realize unless they are really diving into their Googlebot crawl logs to see what Google is calling when, and even then, many only look specifically at pages and not other assets on the site such as images or other files such as PDFs.

If you are looking to speed up the indexing, you can use the Fetch and Submit tool in Google Search Console to submit images as well.  This tool works for images as well as webpages, you simply enter in the URL for the image itself.  However, the usual submit URL limits apply for submitting images as well.

So if you are changing to a CDN or changing the URL structure of images, be aware that Google can take a bit of time to recrawl those images, so if you have images that are ranking well and are very important for SEO and traffic, consider submitting them or at least be aware it may take some time for those images to be added or updated.