Thanos went through several redesigns before his starring appearance in Avengers: Infinity War, but a new piece of concept art has been revealed which shows him wearing a black outfit that never made it into the movie. Thanos was first introduced in one of the post-credits scenes of The Avengers, where he was set up to be the cosmic-level threat that the heroes of Earth would have to face in the future.
Thanos would go on to make brief appearances in Guardians of the Galaxy and during a post-credits sequence in Avengers: Age of Ultron, where he was shown wearing a suit of armor that resembled the first costume that he wore in the comics. When Thanos appeared in Avengers: Infinity War, he quickly lost the armor and wore a new gold & purple outfit that left his arms and head bare. Thanos will of course soon return in Avengers: Endgame.
Thanos' outfit went through a few different redesigns during the pre-production of Avengers: Infinity War, but a new one has been revealed on the Instagram page of Jerad Marantz, who has worked as a character designer, costume designer, and concept artist on movies such as Spider-Man: Far From Home, Black Panther, Doctor Strange, Deadpool 2, Shazam, and Batman v Superman: Dawn of Justice. Check it out below.
The unused outfit for Thanos seen above is a hooded top & pants combination with a hexagram pattern running across it, a set of cloth on his belt that resemble the tassets worn by medieval knights, a set of armor-plated boots, and the Infinity Gauntlet on his right hand. It appears that Thanos was originally going to be sporting a hood, which is a reference to several different outfits worn by Thanos in the comics, one of which is the green-hooded cloak that he wore during the time when he became a farmer and used his old suit of armor as a scarecrow.
Marantz says in the description of the image that Thanos went through several different design changes during the preparation for Infinity War. We previously spoke to Matt Aiken, the VFX Supervisor of Infinity War, who explained that the stylized look of Thanos in the earlier MCU films was a result of how limited his screentime was and how they could afford to give him a grand suit of armor, but they had to simplify his look for when he became a major character, as he would be appearing in hundreds of different shots. The redesign seen above is another example of simplifying Thanos' appearance in order to make him easier to create on the screen. Marantz had previously confirmed that the original Thanos design was eventually reworked into the one worn by Proxima Midnight. Visually, the unused design for Thanos' outfit could've worked just as well as the one that appeared in Infinity War, and it could easily become his new look if he manages to survive the events of Endgame.
Source: Jerad Marantz/Instagram