Texture by durability
Since 1.9 items can have different textures or models depending on their durability. MMOItems supports these custom textures. This wiki page does not show how to setup items with custom textures, it rather explains how you can setup MMOItems to have the custom models you added to your resource pack.
It is almost necessary to read that guide on custom textures first (you don't have to read the CODE part).
I made some very simple sword models you can use during that tutorial or on your server. They have nothing special, just a preview of the possibilities of that powerful 1.9 system.
Once you read the tutorial, create an item in-game in MMOItems to get started. Set your item to unbreakable (it is very important) using the corresponding item option and give your item the durability that corresponds to the one you set in your resource pack. Your item should now load the custom texture you created.