What are images that depict Beowulf as an epic hero?

The epic hero is a literary convention that defines a specific type of character. This kind of character typically possesses a number of particular traits, including some sort of extraordinary ability.
Beowulf’s extraordinary ability is his strength--no man alive, and almost no monster alive, can match it. The most famous image demonstrating Beowulf’s strength comes early in the story when he fights the monster Grendel:

He twisted in pain,
And the bleeding sinews deep in his shoulder
Snapped, muscle and bone split
And broke.

This passage shows Beowulf defeating Grendel. But Beowulf doesn't simply win the battle; he does so in grand style (or we might say, in “epic” style) by ripping Grendel's arm from his body. The image of Grendel's arm slung over a rafter in Herot is one of the most famous in all of English literature.
Another key trait of the epic hero is his embodiment of his culture's ideals. Beowulf, as part of the early Middle Ages warrior culture, shows the courage that was so highly prized. We see this most poignantly in the poem's final battle, as Beowulf and his trusted friend Wiglaf battle the dragon. Beowulf is an old king now, no longer the fearsome warrior of his youth. In this passage, he has been mortally wounded by the dragon, but continues to fight on, with Wiglaf's help:

And Beowulf drew
His battle-sharp dagger: the bloodstained old king
Still knew what he was doing. Quickly, he cut the beast in half, slit it apart.
It fell, their courage had killed it.

This is Beowulf's last act on Earth. Moments later he dies from the dragon-inflicted wounds. But, as we can see, his courage holds until the end.