Looking at it closely (200x) - it looks like they used an impression of a cable knit pattern - same as the white snow on top & bottom tiers. not that I have any idea where you would find a mat with that pattern.
AI was thinking it had to be an impression mat as well but just couldn't see a definite pattern to figure out which type. I just emailed the customer a couple of options that I could do in a snow effect, 1 being in buttercream and the other using sanding sugar and pearl. She called me right back and thinks her daughter won't like either so she will probably be picking another cake. It's just snow, I don't know what's to be so picky about. And to be honest, that pattern doesnt exactly look like snow. Its super cute though. But thanks for the help.
It's so cute, looks like the middle tier is all wrapped up for the cold in a jumper. No idea where to by it from, but it's definitely a cable knit type pattern.