All perfect praise be to Allaah, the Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
It is not permissible for you to put a Christmas tree in your shop because this entails displaying the rituals of disbelief and imitating the disbelievers. The Prophet, sallallaahu ‘alayhi wa sallam, said: "Whoever imitates a people belongs to them." [Ahmad and Abu Daawood] It should be noted that whoever leaves something for the sake of Allaah, Allaah will compensate him with something better. Allaah The Almighty Says (what means): {And whoever is pious to Allaah, He will make for him (a way) of going out, and will provide for him from where he does not expect.} [Quran 65:2-3]
Allaah Knows best.