4 years later and I'm still here trying to make this awesome mod works with the Steam version!
Ok, here is the way,
if you have the Steam Version of Beyond the Sword and want to use this mod:
BE SURE TO MAKE A BACKUP OF YOUR CIV4 GAME FOLDERS, BOTH IN STEAM/STEAMAPPS/COMMON AND IN DOCUMENTS/MY GAMES, IF SOMETHING GOES WRONG YOU'LL BE ABLE TO ROLL BACK TO THE PREVIOUS FILES.
-download the installer
-create on your desktop a folder called "Sid Meier's Civilization 4"
-in this folder create a text file and rename it to "Civilization4.exe" (Be sure to change also the extension .txt to .exe)
-run the installer, when prompted direct it to the "Sid Meier's Civilization 4" folder you created
-the installer will create 3 folders called "Assets", "Beyond the Sword" and "Warlords"
- Inside "Assets" there is one folder called "Art", copy/paste the "Art" folder to this location:
C:\Users\my name\Documents\My Games\beyond the sword\CustomAssets
-Overwrite all files
-Copy the "Beyond the Sword" and "Warlords" folders and paste them to this location:
C:\Program Files (x86)\Steam\steamapps\common\Sid Meier's Civilization IV Beyond the Sword
-Overwrite all files
-delete the "Sid Meier's Civilization 4" folder you created on your desktop with its content
I'm not 100% sure everything is perfect but I played for 4 years, and over 1000 hours on my old laptop with this configuration, it looked exactly like in the screenshots and I never experienced glitches of any kind.
Now I installed it on my new desktop computer and it still looks and works the same
Here are a few screenshots of how the game looks: