boinc/clientgui/skins/Default/skin.xml

<?xml version="1.0" encoding="UTF-8"?>
<skin>
   <en>
      <simple>

         <panel_opacity>180</panel_opacity>

         <background_image>
            <!-- Background Image for Simple GUI -->
            <!-- Recommended total size: 600x750 (to accomodate OS size differences and localizations of text) -->
            <!-- Top banner height: about 68 -->
            <!-- EN-Win total size: about 422x582 as of 6.13.12 -->
            <image>
               <imagesrc>background_image.png</imagesrc>
               <background_color>0:0:0</background_color>
            </image>
         </background_image>

         <workunit_running_image>
            <image>
               <imagesrc>workunit_running_image.png</imagesrc>
            </image>
         </workunit_running_image>

         <workunit_waiting_image>
            <image>
               <imagesrc>workunit_waiting_image.png</imagesrc>
            </image>
         </workunit_waiting_image>

         <workunit_suspended_image>
            <image>
               <imagesrc>workunit_suspended_image.png</imagesrc>
            </image>
         </workunit_suspended_image>

      </simple>
   </en>
</skin>