SnowChillin

Snowchillin displays an overlay over the regular Android UI that is showing falling snow. If you're going easy on the snow falling rate and speed, the snow fall can create a nice relaxing winter or Christmas atmosphere while you're working with your other apps.
In premium version you can even control the properties of snow - the falling rate, speed, snowflake size, and wind direction.
The app is not implemented as a live wallpaper, therefore your are able to combine the snow with your custom preferred wallpaper.
The app size is minimal and it also requires only a couple additional permissions.