I am guessing that you changed the filtering property of the NiTexturingProperty, if you expand the "base" texture under that property it will show the filtering mode, most likely Trilerp, however, I think if you change it to Filter_Nearest it will give the effect you are after, may require testing as I'm not sure that is accurate, but I am pretty sure it has to do with texture filtering bias on weather it will show on top of everything.
The only thing that filter_mipnearest does in my experience is that it makes all of the textures look pixelated. In some versions of Nifskope when adding a map effect, filter_mipnearest is the default filtering mode and you must change it to filter_trilerp. I will have to test whether it shows through everything else when I get home- though I still can't quite figure out what the Op needs it for- swome kind of light haloes that show throw walls? Why on earth would you want any texture to ignore Occlusion Culling?
Anyways some of my favorites.
NiSpecularProperty seems to give cleaner reflections to meshes that use a combination of a gloss map and omnilight env map. Use this in conjunction with modifying the specular amount under the relevant NiMaterialProperty node. IMO high values are usually desirable if you are trying to make a shiny surface, I set mine around 100 to 150 (default is 0).
Adding a NiVertexColor Property to the mesh can be used to change a meshes default vertex lighting mode- extremely useful when used in conjunction with mods that add mapping effects like Glow, bump, env, gloss etc... You must however change the Lighting mode in the relevant Block Details that pop up from LIGHT_MODE_EMISSIVE to LIGHT_MODE_EMI_AMB_DIF.