Here is an Easter Egg from The Avengers: Age Of Ultron I haven't seen referenced anywhere.
Now screenshots are beginning to surface, with a fan posting Ulysses Klaue's file on Reddit (see below).
Not only does the file mention T'Chaka and Panther (T'Chaka is Black Panther T'Challa's father), but also the Bilderberg's.
Here is the relevant transcription:
Ulysses Klaue was an assassin hired to take down T'Chaka at the Bilderberg conference in the case that he refused to negotiate Wakanda's resources including Vibranium. But, Klaue was also there personally, as the Panther killed his great-grandfather in the 19th century while this one was trying to annex Wakanda. He was paid ten million dollars for the kill.
As anyone knows who reads the Marvel Comics, the clandestine group made up of Iron Man, Doctor Strange, Professor Xavier, Reed Richards, Black Bolt and originally Black Panther (BP left early, but returns later), is known as the Illuminati and first appeared in an issue of New Avengers.
Of course, Bendis didn't come up with the name himself, as the Illuminati is a reference to a group of powerful super-secret men who rule the world following the Luciferian "I am god" philosophy.
Now the connection to the Bilderberg Group is that the Bilderberg group is made up of members of the Illuminati who hold an annual meeting discussing the direction the world is to take in the year to come. The group is made up of the powerful elite and are all from different walks of life, philosophy, governments, religions, political parties, but the real kicker is they share the common Illuminati thinking, which is their actual belief, and not any of the aforementioned traits.
Okay, history lesson over, with Marvel referencing the Bilderberg Group in The Avengers: Age Of Ultron, it's possible down the road the Illuminati could be featured in the Marvel Cinematic Universe or maybe even in Captain America: Civil War. Iron Man formed the Marvel Illuminati in an attempt to mold and shape the status of the superhuman world around them. The Illuminati were involved with the after-math of the Kree-Skrull War, Secret Wars, Marvel Boy, The Sentry, The Infinity Gauntlet and other events. Relevant to Civil War is that Tony Stark attempted to sway the members into agreeing with the Superhero Registration Act, but only Reed Richards sided with him.
Obviously, things would be a bit different in the Marvel Cinematic Universe as Xaver and Richards are owned by Fox Studios, but Marvel Studios could easily replace the two. We also see the Klau file makes mention that the Bilderberg meeting seems to be old in nature (older than Tony Stark), which may mean the Marvel Studios Illuminati could be made up of Stark's father, Howard, T'Chaka, Hank Pym, creators of SHIELD, etc.
Some other interesting aspects of the Marvel Comics Illuminati is that the group was responsible for launching Hulk out into space (Planet Hulk, World War Hulk), and Blackbolt disagreed with the SHRA and instead launched a war against the U.S. in Silent War (Marvel has slated the Inhumans movie for a 2019 release).
If anything, it shows that Marvel Studios pays attention to the comics by including the Bilderberg's into their MCU as that is essentially a part of the Illuminati.