All available options will be listed here. These options must be placed under the Options: tag inside your item configurations.

example_item:
  Id: diamond
  Options:
    SomeOption: value

Universal Options

These options are applicable to all items:

Repairable

Sets the repair cost of the item to maximum, making it completely uneditable in anvils and/or enchantment tables.
Will override the RepairCost option.
Defaults to false.

  Options:
    Repairable: false

RepairCost

Sets the repair cost of the item.
If set to less than 0, the vanilla one will be used.
Defaults to -1.

  Options:
    RepairCost: 10

Unbreakable

Sets the unbreakable tag on the item.
Items with this set to true will not lose durability.
Defaults to false.

  Options:
    Unbreakable: true

HideFlags

Hides all the item flags, making things like enchants not visible in the item's lore (please note however that the item will still have an enchanted glow).
Defaults to false.

  Options:
    HideFlags: true

PreventStacking

Prevents the item from stacking to similar items.
Defaults to false.

  Options:
    PreventStacking: true

Model

Sets the custom model data ID for the item.
Defaults to 0.

  Options:
    Model: true

Playerheads

Only applicable to playerhead type items

Player

Sets the texture of the player head.
The value must be the IGN of the target player.
Player heads must use data value 3 for this to work.

  Options:
    Player: Herobrine

SkinTexture

Also sets the texture of the player head, but instead uses a SkinURL.

• Type into browser: https://sessionserver.mojang.com/session/minecraft/profile/trimmeduuidofplayerhere.
• Use http://mcuuid.net/ to find the trimmed uuid of the player.

Player heads must use data value 3 for this to work.
This option also supports hashes.

  Options:
    SkinTexture: eyJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6Imh0dHA6Ly90ZXh0dXJlcy5taW5lY3JhZnQubmV0L3RleHR1cmUvODdlMGFhOTQzM2RiYTliNzU5MzJhMTFkYzk0ZDQwNmJkZTE5ZTg2MzUxNDIxNDkyYjNlZDM3OGM4ZTFhN2NjIn19fQ==

Dyeable Items

Color

Dyes the armor piece to a color according to RGB settings. 0-255.
Alternately can use a predefined color. Found here.
Can pick colors using the Paint program on Windows. Open it up then choose "Edit Colors" to get your RGB value.
Only usable on leather armor type, banners, shields and such.

  Options:
    Color: RED

  Options:
    Color: 102,102,153

Fireworks

Options for the FIREWORK and FIREWORK_CHARGE items
For Colors and FadeColors, you can specify what colors you want using the format RED,GREEN,BLUE

  Firework:
    Colors:
    - 255,0,255
    - 0,0,0
    FadeColors:
    - 200,0,0
    Flicker: true
    Trail: true

Books

Options for book items

Title

The title of the book.
Defaults to Unknown.

  Title: <green>How to make YouTube Videos

Author

The author of the book.
Defaults to Unknown.

  Author: CarsonJF

Pages

A list, with each entry being a page of the book.

  Pages:
  - "Page 1"
  - "Page 2\n\nwith some other lines"
  - "Page 3"

Examples

ClothSlippers:
  Id: 301
  Data: 0
  Display: '&fCloth Slippers'
  Lore:
  - ''
  - 'So Soft!'
  - ''
  Enchantments:
  - DURABILITY:1
  Options:
    Color: 200,200,200

Lots of possible options included:

TestHead:
  Id: 397
  Data: 3
  Options:
    Player: Rickyling

dat_item_though:
  Id: banner
  Data: 4
  Display: '&c&lThe Banner&r'
  Lore:
  - ''
  - '&rIt<&sq>s the perfect stone.'
  - '&cNever question that.'
  - ''
  Amount: 8
  Options:
    Color: 200,200,200
    Unbreakable: true
  Enchantments:
  - DURABILITY:1
  - ARROW_FIRE:10

An example of a firework rocket

FireworkGoBoom:
  Id: FIREWORK_ROCKET
  Display: 'Rocket'
  Firework:
    Colors:
    - 255,0,255
    - 0,0,0
    FadeColors:
    - 200,0,0
    Flicker: true
    Trail: true