When Picard consults his computer and he find the image of himself as Locutus, you can see in the image the frame of the D's viewscreen. So someone on the bridge must have taken a photo of the screen.... ITS THE FUTURE!!
Maybe their screen recorder software was under maintenance at the time, so nameless crew member #2's responsibility was exactly to record everything as shown on the viewscreen They still have physical photographs in THE FUTURE, so they must have some personal devices that record video and/or take pictures.
Could have been the ship's flight recorder of the bridge, like what they were able to do in TOS in "Court Martial".
Were all those images from past episodes/movies? Where was the Romulan meeting from? They had their puffy-shoulder silver TNG outfits. Also, where did the Paris shot come from?
The one of the Enterprise E and the Borg cube I get since that will be visual sensors but the close-ups were odd. Especially the Locutus one. Riker must have taken it. That was from a DS9 episode.
The Romulan meeting was from Inter Arma Silent Leges. The Paris shot was from Homefront/Paradise Lost.
Although clearly the Enterprise-D, Locutus did appear on all the Wolf 359 ships too as per "Emissary". So maybe Admiral Hanson was like, "Holy shit let me get my camera" just before the shooting started.
It's a copyright claims issue. Images sent directly from the Borg ship belong to the Borg Collective as a whole, even if they are unclaimed, but images taken on the Bridge itself belong to the Federation, and are usable (with licensing/permissions) by Federation citizens. Screenshots from the events of Wold 359 should be released into the public domain 75 years after the destruction of the Borg Collective.