After switching to a CDN I noticed that my indexed image count went down. I have close to 1000 images on the site with correct tags, alt tags, and all of that. Only 50 are actually being indexed in the organic search. It's a WordPress site with Yoast SEO plugin, using Maxcdn as my CDN. 
Google indexing fewer images after switching to CDN
images;indexing;cdn;google image search