The black areas would only be transparent if the original picture file has black set as the transparency colour (an export option) or if you set entityBlend mode 3.
If I understand what you are trying to do you are using a map to set where you want a conventional texture to be drawn? I'm not convinced that would work tbh, I dont understand how you would combine the alpha 'map' of each texture with the texture itself.
If I understand what you are trying to do you are using a map to set where you want a conventional texture to be drawn? I'm not convinced that would work tbh, I dont understand how you would combine the alpha 'map' of each texture with the texture itself.