It seems that the assumption is that the fourth Avengers superhero will use the time-traveling theory to correct what Thanos had created in the movie Avengers: Infinity War.

When the user names SuperheroNick Noticing something from the figure of Gamora, played by actress Zoe Saldana, by comparing the Guardians of the Galaxy movie poster that was released in 2014.

Compared with the image that the girl Soe Saladan photographed playing with the nebula played by Karen Gillan (2017), it is seen that Gamora is wearing a necklace. In the movie Avengers: Infinity War, the character does not wear the necklace.

Confirm time travel in the Avengers 4?

It is speculated that the image that the pair will be photographed during the filming of the movie Avengers, the sequel to the movie to play with the issue of time travel back to the time when Gamora still wearing a necklace. The neck is there.
Gomorrah in Avengers: Infinity War

The two images are not clear. It may be possible for Gamora to wear this set in a flashback backdrop. But it was cut off and not used in the movie, it is possible.

In line with one of the interesting comments of the people named Jakob535 stated that we are not sure. I think it would be a set that she put on the cut scene of the movie Avengers: Infinity War is a flashback scene during Gamora is a loyal and working for Thanos.