minecraft-assets/data/minecraft/painting_variant/skeleton.json

{
  "asset_id": "minecraft:skeleton",
  "author": {
    "color": "gray",
    "translate": "painting.minecraft.skeleton.author"
  },
  "height": 3,
  "title": {
    "color": "yellow",
    "translate": "painting.minecraft.skeleton.title"
  },
  "width": 4
}