code: public static Resource getBigIconResource(CmsExplorerTypeSettings explorerType, String resourceName) {
  
          if (explorerType == null) {
              explorerType = OpenCms.getWorkplaceManager().getExplorerTypeSetting(
                  (resourceName == null) && !CmsResource.isFolder(resourceName)
                  ? CmsResourceTypeUnknownFile.RESOURCE_TYPE_NAME
                  : CmsResourceTypeUnknownFolder.RESOURCE_TYPE_NAME);
          }
          if (!explorerType.getIconRules().isEmpty() && (resourceName != null)) {
              String extension = CmsResource.getExtension(resourceName);
              if (extension != null) {
                  CmsIconRule rule = explorerType.getIconRules().get(extension);
                  if ((rule != null) && (rule.getBigIconStyle() != null)) {
                      return new CmsCssIcon(rule.getBigIconStyle());
                  }
              }
          }
          if (explorerType.getBigIconStyle() != null) {
              return new CmsCssIcon(explorerType.getBigIconStyle());
          } else if (explorerType.getBigIcon() != null) {
              return new ExternalResource(
                  CmsWorkplace.getResourceUri(CmsWorkplace.RES_PATH_FILETYPES + explorerType.getBigIcon()));
          } else {
              return new CmsCssIcon(CmsExplorerTypeSettings.ICON_STYLE_DEFAULT_BIG);
          }
      }
docs: Returns the big icon resource for the given resource.<p>
  
  @param explorerType the resource explorer type settings
  @param resourceName the resource name
  
  @return the icon resource