The textures that came with your segments for some reason were not sent to the proper folder that the segment scripts are looking for them in. Meaning, open the FPI file for one of your segments, and make sure the script is using the right path to find the texture.
Example:
texture0 = texturebankww2floorsconcretef_e_01_d2.tga
textured0 = texturebankww2floorsconcretef_e_01_D.tga
texturen0 = texturebankww2floorsconcretef_e_01_N.tga
textures0 = texturebankww2floorsconcretef_e_01_S.tga
^That means the segment is looking for the f_e_01_d2.tga texture in the ww2/floors/concrete folder in the texture bank. If the texture wasn't in that folder, then the segment would appear white.
All you have to do to give segments your own texture is put your texture in the correct file, and change the path (above) to 'call up' your texture for the segment.
Success is not final--failure is not eternal.