CSS GUIv0.0.61PropertiesGitHub
Border Image

Border image slice
Border image width
Border image outset
Border image repeat
Border width
Padding

“The parameters comprise sequences which are theoretically infinite but limits are, of course, set to them in practice. There is an upward limit to size and certainly a downward one... Within these sequences there are reasonable bounds; extremes set by technical and functional experience”

In Designing Programmes by Karl Gerstner

.css-gui-element {
  padding: 64px;
  border-style: solid;
  border-width: 128px;
  border-image-width: 128px;
  border-image-outset: 0px;
  border-radius: 0px;
  border-image-slice: 1;
  border-image-source: url(https://source.unsplash.com/random);
}