Different devices can support different sized touch icons - see the iOS developer documentation. Paths must be relative to your theme folder.
A plain set of icons are included by default that use the App Icon Template.', array('!apple_docs' => 'https://developer.apple.com/library/ios/documentation/AppleApplications/Reference/SafariWebContent/ConfiguringWebApplications/ConfiguringWebApplications.html', '!icon_template' => 'http://appicontemplate.com')),
'#weight' => 10,
);
$form['at']['ati']['icon-paths'] = array(
'#type' => 'fieldset',
'#title' => t('Touch Icons'),
);
// Default
$form['at']['ati']['icon-paths']['icon_path_default'] = array(
'#type' => 'textfield',
'#title' => t('Default: 60x60'),
'#description' => t('If you only enter a path for this size it will be used by all devices.'),
'#field_prefix' => $theme_name . '/',
'#default_value' => check_plain(at_get_setting('icon_path_default')),
'#states' => array(
'required' => array('input[name="enable_apple_touch_icons"]' => array('checked' => TRUE)),
),
);
// iPad (standard display)
$form['at']['ati']['icon-paths']['apple_touch_icon_path_ipad'] = array(
'#type' => 'textfield',
'#title' => t('iPad: 76x76'),
'#description' => t('Apple touch icon for older iPads with standard displays.'),
'#field_prefix' => $theme_name . '/',
'#default_value' => check_plain(at_get_setting('apple_touch_icon_path_ipad')),
);
// iPhone retina
$form['at']['ati']['icon-paths']['apple_touch_icon_path_iphone_retina'] = array(
'#type' => 'textfield',
'#title' => t('iPhone Retina: 120x120'),
'#description' => t('Apple touch icon for iPhones with retina displays.'),
'#field_prefix' => $theme_name . '/',
'#default_value' => check_plain(at_get_setting('apple_touch_icon_path_iphone_retina')),
);
// iPad retina
$form['at']['ati']['icon-paths']['apple_touch_icon_path_ipad_retina'] = array(
'#type' => 'textfield',
'#title' => t('iPad Retina: 156x156'),
'#description' => t('Apple touch icon for iPads with retina displays.'),
'#field_prefix' => $theme_name . '/',
'#default_value' => check_plain(at_get_setting('apple_touch_icon_path_ipad_retina')),
);
$form['at']['ati']['icon-paths']['icon_rel'] = array(
'#type' => 'checkbox',
'#title' => t('Use apple-touch-icon-precomposed'),
'#description' => t('Use precomposed if you want to remove icon effects in iOS6 or below. The default is apple-touch-icon. '),
);
}