[andmarios]

Although it is not clear from the blog post, I think what the author did, was to use an old technique for blogs, where you would serve images under many different subdomains. You did this in order to force the web browsers to deeply parallelize the requests, as browsers used to limit to around 4 concurrent requests per domain IIRC. This was pre-HTTP2/QUIC era, and it made a huge difference, as a website could have tens or hundreds of requests per page.

There were even specialized wordpress plugins to take care of this. You just assigned multiple subdomains to your website and the plugin would round-robin the subdomain each image would come from.

If this is indeed the case, then we are in a gray area, where he did and did not violate cloudflare's rules at the same time.

[celsoazevedo]

I don't think it's that. OP seems to have a CMS (LucentCMS) and some sites using it (eg: kritikos-sm.gr) load images from a sub domain (eg: images.lucentcms.com).

While the CMS website receive normal visits and serves HTML content, for Cloudflare it's being used mostly to serve images, breaking their ToS. If the customer website was behind Cloudflare and they used their own (sub)domain to serve images they'd probably be fine because that domain would be serving a healthy mix of HTML and media content.

I think both OP and Cloudflare are in the wrong here. OP was using the wrong product for this and Cloudflare didn't give him time to fix the problem, losing a customer in the process.