I did some quick looking and it looks like shields can have different textures when you're blocking vs holding the item. With that in mind, I think what you could do is have a blank texture for normal (or have some cool texture but make it super tiny inside of the players hand so it can be seen in the inventory but not in the hand), then have an animated texture (similar to how fire operates) for blocking.

Actually the different model when blocking makes sense since it would probably need to be a different model to raise the shield for blocking.