He is talking trolling about embedded images that are server-side. Even if this is possible somehow (I doubt it) then the server will fetch the image using Tor network and our "genius" will see Tor exit node's IP address in his logs. His posts at the end sound hillarious. How can someone know about all this stuff and have completely wrong understanding even in the basics? Maybe he is a so called "white hat" who just finished 5 year training in computer security?
Not necessarily. Unless the website software is specifically coded to use Tor for its own requests it'll send them over the open internet - and since the site will appear to work fine even if the admin screws this up, there's a good chance that some Tor hidden services are actually misconfigured in this way. (Setting up a Tor hidden service that forwards to the webserver and making sure the webserver itself sends out its requests over Tor are totally independent of each other.)
Now, it's possible to set up your server so that the software running your hidden services can't access the internet except over Tor, but it's fairly non-trivial. The easiest method involves obscure iptables matching rules.