Team Insignias are a new kind of items that will be added in the game.
As mentioned by Doomsaw:
They will be rarity find.
They work just like the 5 other basic slots: They have different rarities - green, blue and rare.
They are a new slot with very specific functionality (each insignia has an Aura).
Each has an aura corresponding to the hero they are inspired by.
Example of these insignias are marvel related groups and organization such as the Avengers, X-Men and S.H.I.E.L.D. (anyone can use SHIELD insignias)
Each has a number of affixes based on their rarity (green, blue, purple, etc.)
List of Team Insignias