Must be something peculiar about certain system 18.104.22.168 updates. I updated from 22.214.171.124 to 126.96.36.199 and have no problem with displaying Bmps, Docs or Pdfs. All of these files are located in the scenario folder along with the scenario file. No need to put anything other than graphic files in the override folder.
There is no 188.8.131.52, only 184.108.40.206 and 220.127.116.11. If you updated from older versions (prior to .20), you probably have the old files in the Documents folder still there, so they show. The bug is that the game won't read the files from the Program Files (installation) directory. So a workaround similar to what Lobster said is to copy the the full Scenarios folder from Programs to Documents. Creating separate folders in Graphics Override per scenario would be a mammoth task.
Anyway, a workaround isn't really what I'm asking for (I already know this), and I'm not going into that endless discussion again... I'm just wondering if another patch is in the works to fix this bug (and the others reported after the .40 patch).
Because of the issues with the latest patch I think the next 'path' should not be a patch but a full release. Just tell everyone, uninstall everything TOAW 4 related, make a backup of any edited scenarios, and install the new stand-alone version. Theoretically, that should solve these issues. Steam can probably do this automatically and even the installer of the patch can do it. But hey, I know nothing.