div.sender-avatar[title^="@nex"] {
  background: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' height='500px' width='500px'><text x='0px' y='400px' fill='red' font-size='420px'>🐟️</text></svg>");
  background-size: contain;
  > img {
    visibility: hidden;
  }
}