Would it be possible for the user, as well as providing their own skin packs for the NPC's, to also be able to provide shield textures too? At the moment the ones in the AW mod are pretty basic, so I replace them within the mod jar with my own custom ones.

Ok will give it a try

closing

Resource packs should be able to install and work like minecraft ones.
Except resources should be under 'ancientwarfare' domain path.
For shields:
/assets/ancientwarfare/textures/items/npc/_shield.png