Most .bwm files in mods are unused files by Lionhead that have been swapped with the current ones (that are used by default) to give units a new look. For example, if the bwm file that was used by the game was called "m_usedbygame.bwm" and i wanted to swap it with an unused file, (m_notusedbygame.bwm) then i'd rename the second file to look like the first file, and the game would read that file instead. This is quite funny to work with at first, because you can swap the standard weapons with beer tankards or walking sticks, or swap the standard soldiers with children or llamas :laugh2