I think you get the pointer of the effect structure when you are using material events. But i think it was only possible with the engine sdk not with the plugin sdk.
Also you could include several textures in one big texture. I did some weeks ago, its ok for rather new 3dgfx cards, but slow on older ones.
Its easy to get the effect pointer in a render event, i just didnt see the engine variable even though i looked before It is possible with the plugin SDK, just do this: