13 Biggest Avengers: Infinity War Mysteries

Thanks to a notice from Project Casting, it seems The Russos are looking for alien extras for Infinity War, which is not wholly surprising, even though it was widely presumed to be set on Earth mostly, but the description seems to suggest a familiar race:

"Aliens: We are now taking submissions to be considered for a fun background role on this upcoming movie. Looking for men and women, all ethnicities, who appear 18 – 50’s, who are TALL with a SLENDER or athletic build. MUST be comfortable being PAINTED (including on your face & any exposed body parts). Also looking for people willing to have prosthetics applied to their face, in addition to being painted. Bumps will be provided for makeup & prosthetic applications."

Could that be pointing towards the return of the Chitauri - previously seen in The Avengers - as Thanos' cannon fodder? Are they still waiting to do his bidding even though The Other is dead? Or are we going to see a wholly new alien race dropped in, since the Chitauri were previously motion captured?

Either way, the question of which mysterious aliens this refers to is a big one.