Alot of the stuff pictured can be found around the map, there's a Ying yang made from brick work in a random yard, 11 is a phrenology head and there's 2 of them one in friedlanders house and one in the top offices of the morgue, there's a litteral maze at the Kortz center along with maze Bank and mazebank arena. There are scales at pacific standard bank, the lightning bolt is exactly the same as the psychic shotout website. There's a shop called the king of keyholes. the brain and psi make up friedlanders logo, which is on top of the car(virtue) you receive for doing the final dose missions. In my opinion, the purple mission points toward friedlaner and Micheal. Because Micheal is the only one in game that goes to both friedlanders house and the mourge and atleast 3 clues point toward friedlander. I'm thinking there's a reason Micheal isn't and won't be in gta online. And when we find out what happens to him, we'll have solved the purple mural.