Christmas In Prague is a simple desktop gadget which displays a mildly animated Prague cityscape along with a countdown of the days until Christmas.
Somewhat surprisingly, there's no adware here, no installation required: just unzip the program, launch it, and the animation appears on your desktop. Snow gently falls, the sun rises and sets, buildings light up at night, the moon rises, it's all very nicely done.
Right-click the image and there are various configuration options. You can change the speed of the animation, turn the snowfall on and off, perhaps have it count down to New Year rather than Christmas Day.
The gadget is still a little intrusive, at least by default: it sets itself up to launch along with Windows, and always be on top of other applications. But fortunately these settings can be changed, too. If they annoy you, right-click, clear "Start with Windows", then select Options and uncheck "Always on top"