<Page xmlns="http://schemas.nativescript.org/tns.xsd" navigatingTo="onNavigatingTo">

  <StackLayout>
      <Button class="btn" />
      <Button class="btn btn-scaled" />
  </StackLayout>

</Page>

.btn {
    background-color: orange;
    background-image: url("res://play");
    background-position: center;
    background-repeat: no-repeat;
}

.btn-scaled {
    transform: scale(0.5, 0.5);
}