Let me refine my statements:
The christmas tree isn't a biblical element. It was added to the christmas tradition about the same time it was secularized (if that's a word). Right along with Santa Claus & raindeer. I guess it now could be considered a christmas element in that most churches do decide to decorate with christmas trees, and have therefore assumed it as a christian symbol.
The candy cane however has a direct relationship with st. Nick. I forget the details of the story, but I do know that it is an element of Christian heritage.
The menorah is as much as christian symbol as it is jewish symbol if I have my history correct. Christians don't feel it is as important to them as other holidays, and therefore tend not to celebrate the event (same as passover), yet it is still a christian event. The menorah has the most religious backing as any other symbol suggested here.
Kwanza is not a religious event, and therefore could freely be represented by an icon. I personally don't feel the event has enough importance to be represented by an icon, but it also doesn't apply to me. I personally just feel it is a holiday made up as an alternative to christmas, but that's just my personal feelings.