EpicBackpacks

Download the backpack plugin here

To create backpacks that will use ItemsAdder texture you have to open backpacks.yml (in EpicBackpacks folder) and add this (one for each backpack you want to create):

 cool_backpack:
    display_name: '&fCool Backpack'
    item:
      type: ITEMSADDER_ITEM
      name: "itemsadder:plastic_bag"
    size: 3
    craft_recipe:
      pattern:
        - XXX
        - LCL
        - XLX
      ingredients:
        L: LEATHER
        C: CHEST