mastodon/app/javascript/styles/mastodon/messaging/contacts.scss

.contact-list-container {
  overflow-x: auto;
}

.contact-list {
  display: block;
  padding: 1em;
  min-height: 5em;
  list-style-type: none;
  color: white;

  .contact {
    margin-bottom: 0.5rem;
    img{
      max-width: 3em;
      max-height: 3em;
    }
  }
}