The object in question is a DweFacadePartitionRoof with the ID changed so I don't alter vanilla stuff... I wanted to retexture it for a more unique touch to an inerior I was making. At a certain distance it was fine in-game the new texture for a second working fine. But both in the window view of the construction kit, and very close to it, it turned pure grey. If it's important for some reason, the object is beyond massive set at a scale of 10, to act as a roof for a very large interior area. Even the size 1 version is still pure grey on the construction kit, so I don't think that's the reason why.
Does something that can easily be altered in the mesh of the object interfere with non-default textures? Am I going to have to use an identical mesh with a texture added by nifskope? Will that likely work? Or is it likely something else? (FYI I have basic retexturing knowledge, I'm no master artist of retextured masterpieces, but I know how to rexture objects, even creatures if Skyrim's creature texturing mechanics are similar enough to Fallout NV that is).

What's the cause of this? What do you do with objects with meshes you want a new texture over that insist on being textureless if you alter them? Is Nifskope the solution to this, or is it more complicated?... I updated Nifskope and attempted the trick that allowed me to rexture furniture in Fallout NV... The object in the window appears to be it's vanilla texture, ingame it alters between the altered texture, and the vanilla rexture. So can anyone tell me what's going on? Edit: I simply changed multiple parts of the textures on Nifskope, and that appears to have fixed the problem. Just having one texture slot filled on nifskope didn't seem enough to overrun the default texture, so it appears everything is running fine for now.

Really basic question, I'm just asking to cover all the bases: Does your new texture have mip maps?

Not sure... I use gimp, at the moment I mostly recolor, and make mild changes in part due to medicore or less than medicore texture making skills. On that note, I think I solved the problem though, I'll clarify with an edited post.

When you save your .dds texture file in Gimp, you should see a small popup window asking if you'd like to generate mipmaps, what file compression you want to use, and so on.

Mipmaps are important when it comes to object viewing distance. The farther away you are from the object, the smaller the mipmap that is used. It helps the renderer not die from pixel overdose, especially for larger objects at a distance.

Just... be careful with that all of that map swapping. If you see something like a _m or _n at the end of the texture file path, then its a special map meant to be read by the game differently than a diffuse map, the main texture map.