On the site I've found it they said that the drawings were "sketches of macabre figures that dealt with violence, pedophilia, sexually, etc".
Then I've found it: The Jim Morrison Limited Edition Lithograph Sets and I keep myself asking about the authenticity of this material. I don't really know if we can trust on this, but it seems kinda... True. I don't really know what think about that, but I'll leave it for you to see: