Right now the Facebook API is returning a URL like this with all post/album images 130x130 pixels in size:
https://fbcdn-sphotos-h-a.akamaihd.net/hpho
https://graph.facebook.com/{object_id}/picture?type={thumbnail|album|normal}
Example (using a bogus object_id of 122233334444555):
https://graph.facebook.com/122233334444555/picture?picture?type=large
Make sure object_id is not just the id of an item but it's object_id (which is typically the number following the underscore in the full id).
I got those type values from a helpful facebook response message that said:
"message": "(#100) type must be one of the following values: thumbnail, album, normal"
In place of ?type=... you could do height/width as well:
?width=543&height=543