I suppose all this could be simplified by just not using a separate subdomain 🙃 for the CDN.
But I am curious what your team ends up saying about the canonical link for the image. Did you hear anything back from them?

The thought was portability/not setting up our small business client sites for de-indexing of images if they turned off the CDN or switched providers altogether and also some benefits for indexing. From what you're saying, it sounds like the extra thought and step here might be unnecessary at best?

We worked with that CDN provider to add the link canonical header, and ever since the vast majority of images get indexed correctly from the www version. Will a site:cdn.ignitingbusiness.com search on Google images successfully reveal which image assets are indexed on the CDN?

engines of indexed image assets as a result of a cdn cache purge or other cdn availability 3) if the cdn was ever removed/disabled the images would not have to reindex on. Prior to using the link canonical header with a different CDN provider, most assets where indexed on the cdn URL.

Right, that setup was intentional (inserted into website img src via cdn.), but our goal was still that the image itself would get indexed from the www. version not the cdn. subdomain. Intent was three-fold 1) to get all assets indexed from the primary domain 2) avoid any recrawl issues by search

Let me know what your team says as well regarding the link canonical header usage. This is something that good chunk of cdns support when serving assets from a subdomain. Either way this all supports your original point of having the custom host name for assets in GSC as well 😀

I see what you mean. But at the same time, that's how we can serve the images from our CDN. I'm curious what images you saw indexed from cdn.ignitingbusiness.com in the index, since that's what we were trying to avoid with the link header and have reason to do so in the past.

use rel=canonical, but we've used this canonical header (still only a hint/suggestion of course) successfully to get origin images indexed instead of images on the cdn. See attached image as an example. I appreciate your insight and help understanding this as multiple CDN's have this feature.

I'm a little confused by this. The images on the CDN are shown within the site & can be scraped and indexed by Google right? But we want the original image on the origin server to be indexed. That's where we introduce the link with rel="canonical". I know you're saying that images don't...

@johnmu.com to confirm, your advice includes that CDNs should also be added to GSC given they are hosting assets, correct? This still applies even if all CDN assets have proper canonicals to the asset on the primary site? (e.g. cdn.example[dot]com/manchego.jpg points to example[dot]com/manchego.jpg