I think you can use a http://www.creationkit.com/TextureSet. Someone else can provide more detail.
That's exactly how you do it.
Edit:
Ok, I probably should have written something more than that for the benefit of the OP...
Here's a quick and dirty, which you will have to do for each piece of armor/weaponry:
* You identify the armor you want to retext and make unique, say, the regular steel.
* So, you get both the texture and normal map for it, and move them to data/textures/armor/myarmor/. You will need to do this for both male and female armors, should you want nboth versions to be re-texted... most of the times, male and female armor textures are different.
*In the CK, you go to Miscellaneous > TextureSet. Right click on right panel, select new, give the texture set a name, like MySteelArmorTextute. Click on difuse, and find the texture in data/textures/myarmor. Click on Normal/Gloss, and find the normal map in /data/textures/armor/myarmor. Click OK.
* Go to ArmorAddOn, and click on SteellCuirassAA. This is what your character is actually going to wear. On the ID window, give it a name, like MyArmorAA. On the left, you will see Biped Model and First Person under Male and Female, respectively, and the path to the mesh for the cuirass. One each of them, you are going to do this:
- click on select. A window will pop up with the armor on the left. On the right, you'll see a window named Alternate Textures.
- Double-click on each, and find your texture set in the list and double-click it. You should see the armor change to your texture.
-Once you are done, click Ok. Again, repeat this with the other models.
* Click OK, a message wil ask you if you want to create a new asset, click ok.
*Now go to Armor > Steel. Double-click on ArmorSteelCuirassA.
* In the ID field, give the armor a new name, like MySteelArmor.
In the middle of the window, you'll see another Male and Female sections. These are the icons you are going to see i your inventory when you select the armor. DO the same thing you did previously with your texture set(s).
*Lastly, underneath, there is a Models window that should say SteelCuirassAA. Right click on it and delete it. Right click again, select new, and find MyArmorAA. Click OK, when ask if you want to create a new asset say yes.
Done.