It looks good, although I personally prefer to create and use a dictionary helper function:
<?php echo dictionary("showcase_li2"); ?>
which allows you to easily switch methods later and gives you more control over your dictionary. Also with the array you will have a problem with the scope - you will have to import it into each function, using a global $language;very annoying one.
You will probably also reach the point where you need to insert values into an internationalized string:
You have %1 votes left in the next %2 hours.
Sie haben %1 stimmen übrig für die nächsten %2 stunden.
Sinulla on %1 ääntä jäljellä seuraavan %2 tunnin ajassa.
Something helper function can be very useful for:
<?php echo dictionary("xyz", $value1, $value2 ); ?>
$value1 $value2 %1 %2.
, func_get_args().