I think the problem may be with your game's settings. All textures should be visible. There are a couple of things you should do before blaming the error on IDF....
If you downloaded the mod anytime after the 15th of November, you should be fine. If you got it before that, you still shouldn't have the problems you described.
1.Make sure IDF is the highest priority mod in the list, in other words, it should be on the bottom. If other mods are interfering it may not work correctly.
2.Make sure your copy of GR is patched to at least version 1.3. If it isn't, get the latest patch from redstorm.com.
