A nativity element that is taken way beyond its context is the star of Bethlehem. It’s Christmassy because it shone done on baby Jesus and showed the three kings where to go but stars are used by themselves all over the place with nary a stable in sight: on wrapping paper, on plates, on mince tarts, wherever you look.
So if you’re not Christian but don’t mind referencing Christianity in a mild way, feel free to use stars on your own gift tags and cupcakes.
Angels are more religious, not so much because they heralded the birth and told the shepherds where to go but because they haven’t strayed as far from the manger as the stars have. However, there are plenty of angels in the Old Testament so, if you’re Jewish, you could decorate with non-nativity angels.
 I don’t think astral navigation would work so well on a city grid: it doesn’t allow for one-way streets, off-road travel or private property.
 And the pregnancy too, actually – no pharmacy predictor tests for Mary!