discourse/app/assets/stylesheets/desktop/upload.scss

.add-upload .fa-plus {
  font-size: 10px;
  position: relative;
  left: -5px;
  bottom: -5px;
  text-shadow:
   -1px -1px 0 $btn-primary-background-color,
    1px 1px 0 $btn-primary-background-color,
    1px -1px 0 $btn-primary-background-color,
    -1px 1px 0 $btn-primary-background-color;
}

.upload-selector {
  label {
    display: inline-block;
    padding-left: 10px;
  }
  .radios {
    height: 60px;
    .inputs {
      float: right;
      width: 75%;
      input {
        width: 90%;
        margin: 0 0 5px 0;
      }
      input[type="file"] {
        font-size: 14px;
        line-height: 18px;
      }
      .description, .hint {
        color: $secondary_text_color;
      }
      .hint {
        font-style: italic;
        margin: 5px 0 0 0;
      }
    }
  }
  .radios:last-child {
    height: 20px;
  }
}