On the right-hand side of the tableau is the head of a bird of prey, perhaps an eagle.
In another room, archaeologists came across a drawing of a boxing match, with one fighter apparently having just delivered a knockout blow to his opponent.
They also found the outline of three small hands, traced with charcoal.
The delicate line drawings survived the eruption of Mount Vesuvius in AD79 which smothered the Roman town in layers of pumice and ash.
The discovery of the sketches “helps to better understand childhood in ancient Roman times”, archaeologists said.
“The exposure to extreme forms of violence, even for small children aged between five and seven, is not only a problem in our own times with the advent of video games and social media. The difference is that during antiquity, the blood spilt on the arena was real.”
Witnessing such brutal scenes must have had an impact on the psychological health of small children living in Pompeii, archaeologists said.
The drawings are being studied by experts in child psychology from the University of Naples Federico II.
Gabriel Zuchtriegel, the director of the Archaeological Park of Pompeii, said: “In all likelihood, the drawings of the gladiators and the hunters were based on direct experience rather than pictures.
“One or more of the children who once played in the courtyard, between the kitchens, latrines and the vegetable gardens, would have seen fights in the amphitheatre, coming into contact with an extreme form of violence which may have also included the execution of criminals and slaves. The drawings show us the impact of these images on a child of a tender age.”
The stick figures are remarkably similar to the drawings of people that a child might produce today, he said.
Archaeologists also discovered the skeletons of two victims, a man and a woman, who were killed by the volcanic eruption. They were seeking shelter in a narrow corridor when they died.
They unearthed frescoes depicting mythological scenes featuring centaurs, sirens and griffins as well as the deities Apollo, Aphrodite and Dionysus.
Gennaro Sangiuliano, Italy’s culture minister, said: “Pompeii reveals marvellous new discoveries on a regular basis.”
Just last month, archaeologists found wall paintings that depicted the legend of Helen of Troy.
One fresco depicts Paris about to elope with, or perhaps abduct, Helen of Troy, the event which, according to legend, triggered the Trojan War.
Another image shows the god Apollo, largely naked but with a blue cloak draped over his shoulder, leaning on a lyre and attempting to seduce Cassandra, the Trojan princess.