I think only one pic per animal per month. So in other words, not 2 or more pics of the same animal (from different angles and poses).
However two or more different pets by the same owner I think is OK (so like a one cat and one dog by one owner is fine).
Those are my two cents. Does that make sense ?
Edit: Ah I just saw your post above my Angel Lady - if you want to make it one per per person that fine - but I still think it should also be one PIC per one pet per one owner per month.