It's the 2nd line I think on item_kinds1.txt. To be able to change an item's texture without merely overwriting the normal texture, you have to add various references (sometimes upwards of 5-6 in different files) to different .rsf files. My advice is to just make your texture and either submit it to me for the next version of HugeMod, or wait until I put out an RSF editor (eh, might be soon, might not, I'm moving right now so it's pretty busy).
Edit: So make your textures now, and test them by just replacing the default ones, make sure they work and have proper shininess (that delayed HugeMod v2 and Mag7 for ~1 month, because of shininess issues) and then let me know about them or wait it out(editor).