تصويرون

<img src="..." class="img-fluid" alt="...">

<img src="..." class="img-thumbnail" alt="...">

<img src="..." class="rounded float-start" alt="...">
<img src="..." class="rounded float-end" alt="...">

<img src="..." class="rounded mx-auto d-block" alt="...">

<div class="text-center">
  <img src="..." class="rounded" alt="...">
</div>

<picture>
  <source srcset="..." type="image/svg+xml">
  <img src="..." class="img-fluid img-thumbnail" alt="...">
</picture>

$thumbnail-padding:                 .25rem;
$thumbnail-bg:                      $body-bg;
$thumbnail-border-width:            $border-width;
$thumbnail-border-color:            $gray-300;
$thumbnail-border-radius:           $border-radius;
$thumbnail-box-shadow:              $box-shadow-sm;