Give another ending to the gift of the magi?Give another ending to the gift of the magi

Of course, since this is fiction, you can have any ending
you want to the story.  You just have to decide what point you are trying to make in the
story.  O. Henry has it end the way he does because he wants to discuss the nature of
true love and he wants his characters to show what people do when they are truly in
love.

But if you wanted to show that love and life and all
of that is futile, you could have space aliens destroy the city just as Jim and Della
come to deal with what they have done.

Perhaps more
plausibly, you could have one of the two of them be horrified at what the other has
done.  You could have them be angry that the other has spoiled the gift that they
sacrificed for.  This would show them in a much more negative light and would suggest
that people are inherently selfish.

So you really need to
just decide what message you want the story to send and then think of an ending that
would convey that message.