border-image-source

border-image-source: url("/shared-assets/images/examples/border-diamonds.png");

border-image-source: url("/shared-assets/images/examples/border-stars.png");

border-image-source: repeating-linear-gradient(
  45deg,
  transparent,
  #4d9f0c 20px
);

border-image-source: none;

<section id="default-example">
  <div id="example-element">This is a box with a border around it.</div>
</section>

#example-element {
  width: 80%;
  height: 80%;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 50px;
  background: #fff3d4;
  color: black;
  border: 30px solid;
  border-image: url("/shared-assets/images/examples/border-diamonds.png") 30
    round;
  font-size: 1.2em;
}

/* Keyword value */
border-image-source: none;
/* <image> values */
border-image-source: url("image.jpg");
border-image-source: linear-gradient(to top, red, yellow);
/* Global values */
border-image-source: inherit;
border-image-source: initial;
border-image-source: revert;
border-image-source: revert-layer;
border-image-source: unset;

.box {
  border-image-source: url("image.png");
}