1!Patience's children could see the Sins and Virtues
Although it hasn't been confirmed as hereditary (and might even have been Jossed) It's still a reasonable theory.
Diligence gets really mad when you break one of his "projects"
Thoughts on the possible a-noises (some of) the Virtues make (haven't thought of any for the Sin's yet besides Gluttony's cannon purring.) make when relaxed with thoughts on the animal/nature association already in place.
Humility - A humming, wrring type of sound, like a louder version of the sound of humming bird's wings.
Kindness: Chirps or tweets. Bird noises.
Charity: Speaks whale (or makes dolphin noises) to go with he ocean motif.
Patience: Cricket chirps to go with the mantis limb thing.
Temperance: If he makes any noises, they are not within the human range of hearing.
Diligence: As much as I want to stay with natural sounds, I can't get past the idea of him sounding like a motor.
Chastity: No idea.
Jossed in the case of Chastity and presumably for everyone else.
What weapons and/or fighting style the unreleased Seraph mode Virtues would have.
Kindness: Ranged attacker.
Patience: Possibly subdues opponents by rendering them unable to move lets others deliver the killing blow. Another theory is that he causes status conditions.
Chastity: A shield. Keeps up defenses between allies with barriers and the actual shield.