On FindPenguins we allow you to upload up to 6 photos in each footprint. For our premium members the limit is 10 photos and 2 videos per footprint.
However, as the number of footprints is unlimited to all our users, the number of photos you can upload in total is also unlimited, even as a none premium member.
The reason for a limitation is, that we want you to set footprints for various places: For example a footprint on the beach, one at your hotel and one for the national park nearby.