The image of Death as a little or juvenile, sometimes winged boy who is holding a downwards turned torch was the way the Ancient Greeks pictured Thanatos, God of Death and twin brother of Hypnos, God of Sleep.
At least according to the theories of Gotthold Ephraim Lessing, a German scholar and writer from the 18th century. Whether he was right is still debated among art historians, but the theory itself is still extremely popular.
Be that as it may, the question of "How the Ancients pictured Death" is a little more complex than that. The main ‘problem’ is that they certainly didn’t imagine Death the way we are used to see him, because our view is heavily influenced by Christianity. In a way, our image of Death is still the one that came up at the end of the 14th century, along with Ars moriendi, the story of The 3 living and the 3 dead and the Danse macabre (Dance of Death).
Ancient mythology doesn’t have the one and only (powerful) image of Death. The idea is sort of ’split up’, on one side we have Thanatos, who IS in fact Death incarnate. Yet, his importance among the Gods is nothing compared to Hades, God of the Underworld.
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In case the young lady in the third panel does not look familiar to you: It’s Death from the comic series Sandman by Neil Gaiman (DC Vertigo Comics).
I actually liked the comic, but this oh-so-lovely-goth-chick that happens to be the Grim Reaper… well… she’s quite okay, but a little bit too cute for my taste.