Pagan death rituals are predominantly rafts sent to sea or firey pyres, as seen in Iliad. Beowulf's death ritual was a fiery pyre, as assuredly pagan as is the ritual of piling on of riches. Pagan ceremonies include the belief that souls require possessions in the afterlife. This is opposite to the Christian belief of a possession-free afterlife. Note that Beowulf did not request the treasure be sent with him. He only requested a memorial:
The wise old man
spake much in his sorrow, and sent you greetings
and bade that ye build, when he breathed no more,
on the place of his balefire a barrow high,
The text says he was the mightiest of men while he was alive and "had joy of his jewels and burg"--while alive The Christian element comes in to play (1) at his request for a memorial only and (2) at his warriors' decision to not cast lots for possession of the treasure,
No lots they cast for keeping the hoard
when once the warriors saw it in hall,
and (3) in their decision to put the treasure away again in the safekeeping of Beowulf's burial mound barrow. This is a Christian demonstration of the belief in the immaterilaity of material wealth.
THEN fashioned for him the folk of Geats
firm on the earth a funeral-pile,
and hung it with helmets and harness of war
and breastplates bright, as the boon he asked;
and they laid amid it the mighty chieftain,
heroes mourning their master dear.
Then on the hill that hugest of balefires
In heavy mood
their misery moaned they, their master’s death.
The smoke by the sky was devoured.
The folk of the Weders fashioned there
on the headland a barrow broad and high,
by ocean-farers far descried:
in ten days’ time their toil had raised it,
the battle-brave’s beacon. Round brands of the pyre
a wall they built, the worthiest ever
that wit could prompt in their wisest men.
They placed in the barrow that precious booty,
the rounds and the rings they had reft [taken] erewhile,
[those] hardy heroes, from hoard in cave, --
It is certainly more of a pagan ritual than a Christian-or-later ritual; in fact, it shows connection to the Egyptian practice of filling the Pharaoh's tomb with treasure, food, and servants to assist him in the afterlife. A Christian ritual would eschew sending all the wealth off -- or burying it -- for distribution among the poor, since the dead man has no more use for it in the afterlife (as far as I know there is no Christian tradition that material goods pass with the soul to the afterlife).
The funeral in Beowulf involving the sea is the one at the beginning of the poem -- the one involving Shield Sheafson. (Beowulf's body is cremated at the end of the poem). In both funerals, but especially in the first one, a strong Christian message is implied. For instance, regarding Shield the poet writes, "Shield was still thriving when his time came / and he crossed over into the Lord's keeping." The point of burying him at sea with treasures is to show respect for him -- to show that he means more to his people than the treasures. The same is true of the burial of the treasures at the end of the poem, after Beowulf's body has been cremated. The poet again implies, when describing Beowulf's death, that he has gone to heaven: "His soul fled from his breast / to its destined place among the steadfast ones." (Seamus Heaney translation)
I agree with the above posts, and would add that some of Beowulf's treasures are buried with him (burned) because the warriors that were with him in his final battle against the dragon all ran away in fear and didn't support their king, so they are undeserving of a share of the treasure gained in the battle. Wiglaf, the only warrior to stand by Beowulf's side, is very adamant in his condemnation of the others in regards to their cowardly behavior. They certainly are not living up to the Anglo-Saxon code.
A fundamental point of the story is that there is both pagan and Christian elements. The burial is pagan. There is nothing in Christianity that speaks of burying treasure with the deceased. In fact, it is just the opposite. Job in the Old Testament says that he entered the world naked and naked he will leave the world as well. Also there are many places in the New Testament that speak of the our gold and silver rotting. Hence, there is a strong emphasis on the rejection of worldly treasures.
The way in which Beowulf is buried is certainly pagan. However, the pagans in the epic expected that Beowulf would also have shared the treasure with them. Perhaps you can argue that the burial of the treasure shows that we should not value earthly things. You can argue that Beowulf's actions all protected people from evil (Grendel, dragon). By burying the treasure with him, he is making the point that his sacrifice was to protect the people from evil, not to make them wealthy.
I would have to agree with accessteacher here. The sending off of Beowulf, at the end of the epic, is representative of Pagan practices. Pagans would tend to "leave" the world with their treasures.
I would say it is more of a pagan ceremony myself rather than a Christian one. I suppose in one sense it acknowledges an afterlife and seeks to provide for the dead monarch in that afterlife by sending him off with various treasures. However, the problem with it is that the Christian afterlife is very clear in acknowledging that whatever we accumulate in this world cannot be taken with us into the next, so this is where it seems to be reminiscent of a pagan idea of the afterlife rather than a Christian one.