I'm posting links to access the "high res" versions of the maps for B2: Keep on the Borderlands map.
The link : Google Drive Map Link
The above is the Caves of Chaos section. DM and Player views. They are 16meg each and 14800x10200. Do NOT try and use these maps in FGC. They work fine in FGU for me but your mileage may vary.
I use these larger maps so I can get 100 pixel per 10 ft square or 50 pixel per 5 and decent quality.