Adding your company’s logo to your Christmas cards is entirely up to you. This choice hinges on your business, your intended recipients, and your purpose for sending the cards.
Having a visual representation of your company helps customers associate your logo with your business. This recognition can be especially helpful if your logo does not use your company’s name or any other identifying factors. If this is the case, it could also be helpful to add the company name to be clear. Plus, using your logo makes you look more professional and established. Additionally, if your logo represents many branches, it could help unify your location with the rest.
There is a reason your company has developed a logo in the first place. Maybe it was to better illustrate the type of business you do, to send a subliminal message while marketing (showing compassion, modernity, etc.), or maybe your logo was created to boast a reboot/refresh (new owner or direction). Whatever it is, the point is your logo was formed with specific intentions in mind, consciously or not. Think about if using your logo in a Christmas card could better support your intentions.