Christmas trees are pagan, and should be avoided by Christians.
At first glance, the Bible seems very clear on this.
For the customs of the people are vain: for one cutteth a tree out of the forest, the work of the hands of the workman, with the axe. They deck it with silver and with gold; they fasten it with nails and with hammers, that it move not.
- Jeremiah 10:3-4 (KJV)
A bit like this?
- By Kgbo / Wikimedia Commons / CC BY-SA 4.0
Decorated with silver and gold?
- By Alina Zienowicz / Wikimedia Commons
But the above verse can also refer to an idol being cut from a tree, etc.
Some even say that Jesus was born in September, so I honestly have no idea what Christmas is anymore. You know what I mean? Where did "25 December" even come from?
Things like Sinterklaas or Santa Claus are definitely pagan, I know that at least.
I guess the point is that we can't be entirely sure about the date, so maybe we're not supposed to celebrate it?
Also, anything that stands between God and you, is an idol.