Following the Dan Abnett, Andy Lanning and Jack Kirby Easter Eggs for Guardians of the Galaxy 2, now buddy to James Gunn, Nathan Fillion's own reference is discovered on set.
Fans spotted mock movie posters featuring Nathan Fillion who is featured as Simon Williams aka Wonder Man. Fillion also played an alien in the first Guardians of the Galaxy movie.
In the comics, Wonder Man starred in the "Arkon" movies, which saw the character of same name do battle against Wonder Man and tell Simon not to have the studio do any more films with his name.
Regarding the "Haxan" movie poster, it seems it's a possible reference the 1922 movie of the same name, in which Wiki describes as: "Swedish-Danish silent film written and directed by Benjamin Christensen. Based partly on Christensen's study of the Malleus Maleficarum, a 15th-century German guide for inquisitors, Häxan is a study of how superstition and the misunderstanding of diseases and mental illness could lead to the hysteria of the witch-hunts. The film was made as a documentary but contains dramatised sequences that are comparable to horror films."
The third movie poster looks to possibly be a Tony Stark film with Simon Williams playing the lead character, which might be an Iron Man movie based in the MCU from the events that went down in the 2008 movie.
The fourth poster, "Oh, Rebecca," may be a reference to Fillion's former role on the soap, One Life To Live. Actress Rebecca Budig from the soap has appeared on Fillion's Castle.
You can also check out Guardians of the Galaxy 2 set video from the scene featuring some sort of chase and car crash. Maybe it's Arkon?
"Guardians of the Galaxy Vol. 2" has a May 5, 2017 release directed by James Gunn starring Chris Pratt as Star-Lord, Zoe Salanda as Gamora, Dave Bautista as Drax, Vin Diesel as the voice of Groot, Bradley Cooper as the voice of Rocket Raccoon, Karen Gillan as Nebula, Michael Rooker as Yondu, Sean Gunn as Kraglin, Pom Klementieff as Mantis, with Kurt Russell playing an unknown role.