I don't see a plugin that does that easily off hand, maybe someone can correct me.

Piwigo admin page uses this to generate it:

include_once(PHPWG_ROOT_PATH.'admin/include/functions.php');
$stats = get_pwg_general_statitics();

I slapped together this little plugin that will put it in the footer of every page if you want to try it out, code is super simple and stripped down for easy modification (I broke down Perso Footer plugin to make it quickly for you). You can see it active on the footer of my page currently. Could be updated to also display users and other available keys I put in the comments of the code.

https://github.com/swhite8/piwigo-statfooter