Momento

Configuration:

in plugin config.yml:

chat:                           # for ur emojis and stickers:
  "emoji":
    ":discord_emoji:": "\uE002" # replace with ur unicode symbole
    
  "sticker":                    
    "discord_sticker": "\uE102" # replace with ur unicode symbole

items:
  dirt_shield:
    ItemStack:
      name: "dirt shield"
      material: "SHIELD"
      model-data: 1
    Durability:
      durability: 10000

Texture pack side

Emotis and stickers:

Use a additional texture pack to replace Unicode emojis by images

${texturepack_folder}/assets/minecraft/font/include/default.json

{
    "providers":[
        {
            "type": "bitmap",
            "file": "minecraft:font/custom/emojis/discord_emoji.png",
            "ascent": 7,
            "height": 8,
            "chars": ["\uE002"]
        },
        {
          "type": "bitmap",
          "file": "minecraft:font/custom/sticker/discord_sticker.png",
          "ascent": 7,
          "height": 8,
          "chars": ["\uE102"]
        }
    ]
}

${texturepack_folder}/assets/minecraft/textures/font/custom/emojis/

Shields:

It's a bit challenging, but you'll need to replace the shield override with a predicate check for the custom model data ('modelData' value in the Momento config) within:

${texturepack_foldeer}/assets/minecraft/models/item/shield.json

"overrides": [ 
    {
        "predicate": {
        "custom_model_data": 1
        },
      "model": "item/shield_name"
    },
        {
        "predicate": {
        "blocking": 1
        },
        "model": "item/shield_blocking"
    },
    {
        "predicate": {
        "blocking": 1,
        "custom_model_data": 1
        },
        "model": "item/shield_name_blocking" // It's really important to have two separate models
                                             // One for blocking and another for normal use
    }
]

⚠️ Take a look on momento texture pack shield for the models