Custom Armor

Custom armor uses the vanilla minecraft:equippable component (1.21.2+): any item can become wearable, rendering a fully custom texture on the body - no shaders, no trims, no restrictions on the base material.

Player armor

Each piece is a normal item with an equippable component pointing at an equipment asset:

# items/emerald_helmet.yml
item:
  item: paper
  name: "<g:#89E59D>Emerald Helmet</g:#37C6BA>"
  texture: item/default/armors/emerald_helmet # the inventory icon
  components:
    "minecraft:max_stack_size": 1
    "minecraft:max_damage": 437
    "minecraft:equippable":
      slot: "head" # head, chest, legs, feet
      asset_id: "ecoitems:emerald"
    "minecraft:attribute_modifiers":
      - type: "minecraft:armor"
        id: "ecoitems:emerald_helmet_armor"
        amount: 3
        operation: "add_value"
        slot: "head"

slot: helmet # the libreforge slot, for effects

The equipment asset defines which textures render on the body. It lives at its natural vanilla location in the pack folder:

// pack/assets/ecoitems/equipment/emerald.json
{
  "layers": {
    "humanoid": [{ "texture": "ecoitems:emerald" }],
    "humanoid_leggings": [{ "texture": "ecoitems:emerald" }]
  }
}

With the layer textures at:

pack/assets/ecoitems/textures/entity/equipment/humanoid/emerald.png (helmet, chestplate, boots - the classic layer_1)
pack/assets/ecoitems/textures/entity/equipment/humanoid_leggings/emerald.png (leggings - layer_2)

One asset covers the whole set; every piece points at the same asset_id. For working examples of the equippable component, see the shipped ruby mob armor (ruby_wolf_armor, ruby_horse_armor, ruby_llama_carpet, ruby_saddle, ruby_harness) - player armor works the same way with humanoid/humanoid_leggings layers and your own textures.

Elytra

Elytra work the same way with a wings layer - see the shipped magic_elytra example:

// pack/assets/ecoitems/equipment/magic_elytra.json
{
  "layers": { "wings": [{ "texture": "ecoitems:magic_elytra" }] }
}

Mob armor, saddles, and harnesses

The same component covers gear for mobs - just different slots and layer types. The shipped ruby_wolf_armor, ruby_horse_armor, ruby_llama_carpet, ruby_saddle, and ruby_harness examples cover every case:

Gear	`slot`	Layer type	Notes
Wolf armor	`body`	`wolf_body`	1.21.2+
Horse armor	`body`	`horse_body`	1.21.2+
Llama carpet	`body`	`llama_body`	1.21.2+
Saddle	`saddle`	`<entity>_saddle` (one layer per rideable mob)	1.21.5+
Happy ghast harness	`body`	`happy_ghast_body`	1.21.6+

Use allowed_entities to restrict what can wear it:

# items/ruby_wolf_armor.yml
item:
  item: wolf_armor
  name: "<g:#FA7CBB>Ruby Wolf Armor</g:#F14658>"
  texture: item/mob/ruby_wolf_armor
  components:
    "minecraft:equippable":
      slot: "body"
      asset_id: "ecoitems:ruby_wolf"
      allowed_entities: "minecraft:wolf"

A custom saddle's equipment asset declares a layer per rideable entity (pig_saddle, horse_saddle, camel_saddle, ...) all pointing at your texture - copy the shipped ruby_saddle.json as a starting point.

Tips

The equippable component supports more options - equip_sound, dispensable, swappable, camera_overlay - all in vanilla component format.
Give pieces durability with minecraft:max_damage (plus minecraft:max_stack_size: 1).
Armor values come from minecraft:attribute_modifiers on the right slot, exactly like the vanilla items.