That particular option is only applicable if you use layout='random'
in your shortcode, or if you set Photonic → Settings → Generic Options → Layouts → Image Layout to Random Tiled Gallery.
If you don’t want to use the tiled layout and use the “square” or “circle” thumbnails instead, you can set a shortcode parameter thumbsize='104'
. The permitted values are 32, 48, 64, 72, 104, 144, 150 and 160.
That being said, there is probably a bug in this for generating thumbnails for albums (it works fine for photos). The remedy is fairly simple, just make this your shortcode, and it should work:
[gallery type='picasa' user_id='myown.user' kind='albums' thumbsize='104' thumb_size='104']