<!-- HTML -->

<div class="info-panel">
  … content …
</div>

<!-- CSS -->

.info-panel {
  …
  position: relative;
}

  .info-panel:before {
    content: "";
    display: block;
    width: 10px;
    height: 10px;
    background: url(../path/to/image.png) 0 0 no-repeat;
    position: absolute; top: -10px; right: 10px;
  }