This theme depends on the 'OS_default' plugin. Please download it first:
http://piwigo.org/ext/extension_view.php?eid=497

This theme has a clear blue style, faded background for the bars, rounded thumbnails, and also:
-tooltips are shown for icons (see the screenshot)
-one menu is horizontal
-the menu on the left is dynamic: the block can be hidden or shown by clicking on it
-the menus are shown on every page except photo pages

The dynamic tabs and display of the menus on pages can be customized:
create themeconf_local.inc.php in 'OS_glass' folder and write/customize this:

$themeconf = array(
'add_menu_on_public_pages' => true, # activation
'Exclude' => array('theNBMPage','thePicturePage','thePopuphelpPage',), # Excluded pages
'tab_system' => true, # activation of dynamic tabs
'tab_closed' => array('mbLinks','mbTags','mbSpecials','mbIdentification'), # tabs which are closed when the page is loaded
);

Enjoy!