Before starting make sure all players who are testing the custom texture you are about to make have gfx viewing distance set to > 1500 and object distance > 100m in their graphics settings.
Now create a custom texture - use SetObjectTextureGlobal to add a texture to say a noticeboard. Place a few playable players at a say 100m or less from the noticeboard. Save mission as MP. Start MP mission and get some colleagues to join the available slots. Walk towards the noticeboard and compare what each player sees on their screen. Some might see the custom texture others will not. In some cases the texture might only appear when right next to the noticeboard. Note this does not have anything to do with gfx viewing settings.