Perhaps a way to have a more "pemanent companion"? It may seem pointless since every creatures can be found in the wild, but idk, like some unique interactions based on affection? (Not necessarily sexual, like feeding, sleeping with, playing...)
It would add another layer of gameplay for those who have completed most of the album, and perhaps add possibilities for more pictures
Also, for creatures ideas, I think a bird like lady or an aquatic one (shark, fish, squid...) would fit well.
Thank you for your work and your dedication to your community :D