From Facebook Developer Wiki

the 'square' size seems to be defunct --509775704 10:52, 10 September 2008 (PDT)

the 'album' size is returning "normal" 600+ pixels wide photos. I guess the album size is no longer supported. I'm using it on an iframe canvas page. --536286910 00:27, 17 April 2009 (PDT)

This function does not work with new accounts.

Old Account (where image is an integer) works: <fb:photo pid="889487885947003906" size="thumb" />

New Account (where image has other chars) doesn't work: <fb:photo pid="100000185917048_7749" size="thumb" />

PIDs taken from photos.getAlbums() --207100037 11:47, 27 August 2009 (PDT)

photos.getAlbums returns albums, not photos, other than the cover photo ID. Is that what you're trying to render here? What do you mean by old and new "accounts"? Pete (563683308 13:12, 27 August 2009 (PDT))