There are several new .txt documents in the steam files for volume 12 (specifically, the file labelled “formatter”), that, in addition to a full script of the volume, appears to include notes for the artists on the backgrounds and end cards. (To be clear, this is just like. readily available in the files. I didn’t rip or hack anything to find this, you can literally just click on it.)
Special thanks to @eldritchdraaks for letting me know about this!