In the last week of September, it was reported by The Hollywood Reporter that there would be additional filming for Zack Snyder's Justice League in October. At minimum, Ben Affleck, Gal Gadot, and Ray Fisher will be part of this additional photography. However, Henry Cavill will seemingly be absent from filming, which could simply be due to him not being needed on set. As far as fans know, it isn't due to a scheduling conflict either and Cavill himself is still fully supportive of the project.
Considering that shooting was planned to begin this month, it makes the timing of the cinematographer for Justice League posting a photo of a blue screen set quite auspicious.
Cinematographer Fabian Wagner has posted on his Instagram a photo of a blue screen set, likely intended for additional photography for Zack Snyder's Justice League.
While Wagner doesn't explicitly say that this photo is from the set of Zack Snyder's Justice League in his post, it is the only movie on his schedule besides Monster Butler, which is still in early pre-production stages.
WHAT THIS MEANS
This indeed coincides with the previous report of additional photography beginning this month for Zack Snyder's Justice League, which further cements this photo being from that planned shoot. Keep in mind that filming is only planned to last a single week and with them using all this blue screen, it seems even more likely that this will only be for simple pick-ups rather than reshooting of entire scenes.
Regardless, fans should keep their expectations in check and not expect Snyder to be filming large new action scenes or anything too elaborate. At most, they could be completing the filming certain scenes that went unfinished when first shooting the movie way back in 2016.