Baubles are very Christmassy and the good news for atheists is that they mean nothing: the glass blowers of Lauscha in Germany started making them in the 17th century for decorating Christmas trees and we haven’t looked back since. These days, you can still find plenty of glass baubles in many sizes and most price ranges and you can also find a plethora of plastic baubles in a larger range of sizes and a cheaper range of prices.
They’re also a very easy shape to depict on Christmas cards and tags and wrapping paper. (Bear that in mind if you’re keen to make cards, tags and/or wrapping but are not confident of your artistic skills.)
So Christians and non-Christians alike should feel to free to decorate their trees, their houses, their umbrella stands and any slow-moving pets with as many baubles as they can get their hands on. (Christmas is not a time for restraint.)
 I used to be snobbish about the plastic ones but they really do look good, and they don’t shatter into dangerous shards when you drop them so now I prefer them.