AdminLTE/scss/dark/bootstrap/_images.scss

// Image thumbnails
.img-thumbnail {
  background-color: $thumbnail-bg-alt;
  border: $thumbnail-border-width solid $thumbnail-border-color-alt;
  @include box-shadow($thumbnail-box-shadow-alt);
}

//
// Figures
//

.figure-caption {
  color: $figure-caption-color-alt;
}