All permanents on the battlefield (Mirror Image as a copy of Cavalier of Night).
.
Steps
Activate Bartolomé del Presidio by sacrificing Mirror Image.
When Mirror Image dies, its last ability from Cavalier of Night triggers, returning itself from your graveyard to the battlefield as a copy of Cavalier of Night.
When Mirror Image enters the battlefield, its first triggered ability from Cavalier of Night triggers; choose not to sacrifice a creature.
Resolve the Bartolomé del Presidio ability from step 1.
Repeat.
Results
Infinite +1/+1 counters on Bartolomé del Presidio.