Google not Indexing images on CDN.

[alphonseha]

My URL is: http://bit.ly/1H2TArH

1. We have set up a CDN on our own domain: http://bit.ly/292GkZC 
2. We have an image sitemap: http://bit.ly/29ca5s3
3. The image sitemap uses the CDN URLs.
4. We verified the CDN subdomain in GWT.
5. The robots.txt does not restrict any of the photos: http://bit.ly/29eNSXv. We used to have a disallow to /thumb/ which had a 301 redirect to our CDN but we removed both the disallow in the robots.txt as well as the 301.

Yet, GWT still reports none of our images on the CDN are indexed.

The above screenshot is from the GWT of our main domain.The GWT from the CDN subdomain just shows 0. We did not submit a sitemap to the verified subdomain property because we already have a sitemap submitted to the property on the main domain name. While making a search of images indexed from our CDN, nothing comes up: http://bit.ly/293ZbC1While checking the GWT of the CDN subdomain, I have been getting crawling errors, mainly 500 level errors. Not that many in comparison to the number of images and traffic that we get on our website. Google is crawling, but it seems like it just doesn't index the pictures!?

Can anyone help? I have followed all the information that I was able to find on the web but yet, our images on the CDN still can't seem to get indexed.

[alphonseha]

Hey Dan,

Thanks for your concerns. The reason for that is because of the image headers. We display different images depending of the resolution of the user visiting the website. So because of this, the image is downloaded automatically rather than being displayed. I researched on this and this shouldn't be a problem in terms of Image SEO. As for the images and watermarking. That is a business decision.

[evolvingSEO]

Hey There

I just did a reverse image search on two of your images and they are present in Google Image search

• http://screencast.com/t/QWKhqQfIH0Z8 - this one is indexed.
• This one is indexed and both versions are from Eyeem

But one issue, is that when I click 'view image' (what normally would open the image file in a new tab - instead it triggers a download box for me --> http://screencast.com/t/7LyLRRJ4CTb6 - perhaps this is because you are preventing people from doing so and just copying the images for free. But I was actually able to download the image for free straight from Google (the download worked).

Which leads me to another question... if the images are not free, maybe it makes sense to not index them? Or maybe index a watermarked version or small thumbnail?