I'm a "pure" atheist, but I have no issues whatsoever with the term "Angel". It is an appropriate fit with the naming convention used here and it would be my first choice. An alternative suggestion that is less sect-specific to my ears would be "Spirit".
I'm an atheist, too, and I subscribe every single word of your post.
We are metaphoric monks in a metaphoric monastery, so if I agree to be called "friar" now, I should not object to be called "angel" or "spirit" when I'll be dead. Indeed I don't object to it, and certainly I'll not do then.
My materialistic point of view is that I don't know if (and I don't believe that) there is an immortal part of what is me, but I do know that each one of us can achieve a little bit of immortality doing something useful for the others. And useful can be a very wide word.
So, I can't think of anything more appropriate than remember who is no more here by mean of what he did. I'm thinking of a place (a crypt? is it the right word?) to remember them and their work. I'd love to be there when my time comes.
Rule One: "Do not act incautiously when confronting a little bald wrinkly smiling man."
I agree with 5mi11er, this site is a pseudo-monastery. In the Middle Ages, the monks were in monasteries copying and preserving books and knowledge, we maintain the tradition in the modern age..... copying ,preserving, and maintaining code. If you don't believe in the Judeo-Christian ethic, just play along like its a game. I was raised in the Catholic Church, but now I am more of a Bhuddist. So I would say attaining "Angel" level, would be like attaining Bhuddhood, and sitting on a lotus flower in the spiritual realm, radiating positive energy.
But whether you call it Angel, Bhuddahood, TopDog, or whatever; anyone who believes in one God( spirit, etc), should realize it is all the same thing, just filtered thru different civilizations.
If you don't believe in any of it (a pure atheist), you can call it a practical delusion to make life meaningful, the opiate of the people.