Template:PosterGalleryCSS.css

/* Card frame */
.ksi-posters .gallerybox .thumb {
  border: 1px solid #777;
  background: #111;
  padding: 6px;
  box-shadow: 0 1px 4px rgba(0,0,0,.4);
}
.ksi-posters .thumb img { display:block; width:100%; height:auto; }

/* Caption text (non-links) = white */
.mw-parser-output .ksi-posters .gallerytext {
  color: #fff !important;
  font-size: 90%;
  padding-top: 4px;
  text-align: center;
}

/* Keep links using the skin’s normal colors */
.mw-parser-output .ksi-posters .gallerytext a,
.mw-parser-output .ksi-posters .gallerytext a:visited,
.mw-parser-output .ksi-posters .gallerytext a:hover,
.mw-parser-output .ksi-posters .gallerytext a:active,
.mw-parser-output .ksi-posters .gallerytext a:focus {
  color: revert !important;          /* fall back to site/skin link color */
  text-decoration: revert !important;/* keep site’s underline/hover style */
}