Coulson's energy shield comes from the comics. It was used by Captain America when his metal shield was being repaired.
When Coulson (Clark Gregg) is overseeing Operation: Decap (about 37 minutes in), he's handling one of his vintage Captain America trading cards Nick Fury (Samuel L. Jackson) smeared with Coulson's blood in The Avengers (2012).
Hellfire states that he considered "Firestarter" as an alias, but decided against it because it felt "a little 90s". This is a reference to the song "Firestarter" by The Prodigy.
During Talbot's mission, one of the soldier's call signs was Red 6. This can be a nod to the Red 6 pilot call sign from Star Wars: Episode IV - A New Hope (1977), which, coincidentally, has its rights owned by Disney as well.
Mack (Henry Simmons) is in a bar while James (Axle Whitehead) is deciding his villain name. At one point he ponders the name Firestar. That is the name of Foreshadow who, in the comics, served as an Avenger and a New Warrior.