how do I theme rounded corners in Panels 7.x-3.3 I looked through older questions &amp; answers and some examples about styling rounded corners and they seemed valid but when I look into the code in Panels 7.x-3.3 I see an entire function that dynamically generates rounded-corners and tells Drupal where to find the image files. 

I have new image files for the rounded-corners. How do I over-ride this function without hacking the module itself? 

Ex. (This function is in rounded_corners.inc)

/**
 * Generates the dynamic CSS.
 */
function _panels_rounded_corners_css($idstr) {
  $url = panels_get_path('plugins/styles/corners', TRUE);

  $css = &lt;&lt;&lt;EOF

.t-edge, .b-edge, .l-edge, .r-edge, .wrap-corner {
  position: relative;
  /* hasLayout -1 ? For IE only */
  zoom: 1;
}
$idstr .t-edge {
  background: url($url/shadow-t.png) repeat-x 0 top;
  font-size: 1px;
}
$idstr .b-edge {
  background: url($url/shadow-b.png) repeat-x 0 bottom;
  font-size: 1px;
}
$idstr .l-edge {
  background: url($url/shadow-l.png) repeat-y 0 0;
}
$idstr .r-edge {
  background: url($url/shadow-r.png) repeat-y right 0;
}
$idstr .wrap-corner {
  background: #fff !important;
}
$idstr .wrap-corner .t-edge, $idstr .wrap-corner .b-edge {
  height: 11px;
}
$idstr .wrap-corner .l, $idstr .wrap-corner .r {
  position: absolute;
  top: 0;
  height: 11px;
  width: 11px;
  background-image: url($url/corner-bits.png);
}
$idstr .wrap-corner .l {
  left: 0;
}
$idstr .wrap-corner .r {
  right: 0;
  background-position: -11px 0;
}
$idstr .wrap-corner .b-edge .l {
  background-position: 0 -11px;
}
$idstr .wrap-corner .b-edge .r {
  background-position: -11px -11px;
}
$idstr .wrap-corner .r-edge {
  padding: 5px 24px;
}
$idstr div.admin-links {
  margin-top: -14px;
  margin-left: -12px;
}

$idstr .panel-separator {
  background: url($url/shadow-b.png) repeat-x 0 center;
  font-size: 1px;
  height: 30px;
}

$idstr .rounded-corner {
  margin-bottom: 1em;
}

EOF;

  return $css;
}
The functionality you refer to predates common browser support for rounded corners, when images was the only reasonable solution.

Today, I would most likely no use it, but instead implement it with the modern CSS approach.

If you really want to modify the existing functionality though, it's called a Style. You can see this question for details about implementing ctools plugins: What are Ctools plugin (content type, access, etc), and how does one create them?