minecraft-assets/assets/minecraft/atlases/shield_patterns.json

{
    "sources": [
        {
            "type": "single",
            "resource": "entity/shield_base"
        },
        {
            "type": "single",
            "resource": "entity/shield_base_nopattern"
        },
        {
            "type": "directory",
            "source": "entity/shield",
            "prefix": "entity/shield/"
        }
    ]
}