TYPO3 pages/pages_language_overlay erweitern - ext_tables.

// TCA Konfigurationen

/***
 * pages-Tabelle Erweitern
 */
$TCA['pages']['columns']['tx_extendtest_background_image'] = array(
    'label' => 'LLL:EXT:'.$_EXTKEY.'/Resources/Private/Language/extend-pages.xlf:tx_extendtest_background_image.label',
    'config' => array(
        'type' => 'group',
        'internal_type' => 'file',
        'uploadfolder' => 'uploads/pics',
        'show_thumbs' => 1,
        'size' => 1,
        'allowed' => 'jpg',
        'disallowed' => '',
    ),
);

/***
 * pages_language_overlay-Tabelle Erweitern
 */
$TCA['pages_language_overlay']['columns']['tx_extendtest_background_image'] = $TCA['pages']['columns']['tx_extendtest_background_image'];
$TCA['pages_language_overlay']['columns']['tx_extendtest_background_image']['l10n_cat'] = 'media';
$TCA['pages_language_overlay']['columns']['tx_extendtest_background_image']['l10n_mode'] = 'mergeIfNotBlank';