No, the black damage pattern is indeed a texture (damage.tex), but like almost every efx-related texture, it's use is hardcoded. You can add custom efx-textures to mod_ani.efx, so you can use them in efx.ini or mod_efx.ini or in a prt-file to add as a sprite to your weapon, explosion or whatever-effect, but I wouldn't know how to apply the texture to a model. You can replace damage.tex with your own damage texture, of course, but that's about it, I fear.