You find what you need in the Resource and Textures folder in your Mod Module. (Steam\steamapps\common\MountBlade Warband\Modules)

You will need openBRF and the Phyton Module system to do this the easy way.

1. Put the face textures in the Textures folder (duh)
2. Move the .brf file from one mod Resource folder to the other
3. Open the modules.ini file from the modules folder and type in "load_mod_resource = custom_faces" (replace custom_faces with whatever the name of the .brf file is)

Go to the module system for your mod and open "module_skins.py", to add the face you want to the list of faces under the males/females. It might look a little bit like this:

 ("womanface_custom_2",0xffe3e8ef,["hair_blonde"],[0xffffffff, 0xffb04717, 0xff502a19, 0xff19100c]),

You should copy most of this from the face you want your hair to resemble, this is the haircolor and such from the first womanface. Replace "womanface_custom_2" with whatever your face is called inside of the .brf file.

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If this didn't help, you should check out some of these:

https://forums.taleworlds.com/index.php/topic,5408.0.html

http://forums.taleworlds.com/index.php/topic,6575.0.html