Starting with these, (1st and 2nd image) their icons for Der Riese and Shi no Numa, Nacht and Verruckt are in the game files apparently (along with the maps for them) but I need to try a dumped BO2 to sift through the files and verify, sadly Shi no Numa doesn't have a higher quality
This appears to have been for Der Riese additionally too, it appears that a lot of The Giants early marketing reused stuff from the cancelled BO2 remake (like this loading screen on the (3rd image), note the cropped "II")
Now let's address this, the BO2 font is present here (5th image) while the BO3 is here too (6th image) I believe the left was repurposed for the right but this stumps me why is it called "The Giant" and not "Der Riese" this was maybe an early version of the BO3 screen but why the BO2 font
BO2 design map, this is also running in the engine btw, note the BO2 font, this is definitely from the DLC 5 I have not squinted and checked every pixel yet but your free to do so if you wish (also note the date and time, this helps a rough timeframe of development) (7th image)
Design documents, while maybe boring, to me are fascinating, they detail that the BO1 maps where going to be remastered (except for COTD) additionally they where split into 2 groups, with the WaW Maps in 1 and the BO1 in 2, with Kino der Toten being the exception as it would've- (8th image)
-been lumped with the WaW remasters, the documents show enemy types in the maps, concretely confirming the BO1 Remasters too (again except for Call of The Dead likely due to licence bs with the actors)
So in closing
"What's left to find?"
Here's what I could figure
• Other bits of media of the maps running in the engine exist with witnesses saying parts where flat out broken, buggy, and see-through parts and messy textures
• the WaW Maps being in the BO2 files (filed under zm_asylum, zm_swamp, zm_factory and zm_airfield iirc)
• Icons for Nacht der Untoten and Verruckt exist in the files apparently, I need to find decompiled and dumped files to confirm and hopefully find
The original threads have broken links or redacted info that is unobtainable
I found these through a Wayback Machine on a Call of duty dot com forum because those links for these where broken sadly no dice with the other 2 links I found.
And that's everything, I'm exhausted beyond belief but I'm are happy to have found some info, I hope now to be able to uncover more in the future, but I'm very limited in what I could do at the moment. But I wasn't alone on this. a Twitter user named TheDemiSimp also helped me out on this.