Hi Gianluca,
I've woked on 2 moon images series and adapted them for Cumulus.
First set is a common black and white moon phase images series.
the other is a artistic serie of "progressively eaten rotis"
You could try them with your WB2 template as a direct replacement
(as they are the same size), by modifying index.php file, that way:
Locate this line (#131)
<img src="images/moon.bmp"...
And modify it like that:
<img src="images/Moon<?php echo $MoonAge; ?>.jpg" ...
... supposing that you put moon pictures in images folder.
Best regards,
Jacques