Thanks, @jmorga106 and @Orion
@Orion: It´s a simple repeating vertical scrolling with a little sine sidewards moving, consisting of two pictures. You can have a look how it works at the watch itself, inspection mode should be on.
@jmorga106: The snow effect is made with 10 double layer, so 20 at all. I drew them all by hand with different brush sizes and transparency levels.