The keychain page references images but does not link to them:
<p> [...] If <tt>ssh-agent</tt> is already running, <tt>keychain</tt> will
ensure that your <tt>id_rsa</tt> private key has been added to <tt>ssh-agent</tt>
and then set up your environment so that <tt>ssh</tt> can find the already-running
<tt>ssh-agent</tt>. It will look something like this: </p><p>[...]
After that, <tt>ssh-agent</tt> is already running and has your decrypted private key cached in memory.
So if you open a new shell, you will see something like this: </p><p> [...]
In both cases it looks like there should be an image referenced after the text "like this:"
Ah, looks like it should be referencing these images: https://github.com/funtoo/keychain/tree/master/img