Good idea. Some of the metal textures have something beside their name that says like metal1_pulse. Somethin like that anyway. Those ones pulse when you put them in ur map. Happened to me before.
Dude, some of the metal textures have a 'pulse' characteristic. enlarge the texture window so that you can read them better. The ones that pulse are typically the darker pipe textures and will say '_pulse' or something like that in the name.