I did another cake with snowflakes on it this past weekend, which was appropriate since we get a foot of snow the next day.
For this one I used a stencil on the middle tier to paint snowflakes on with diluted luster dust. It gives a nice little shimmer to the side of the cake, but it isn't too over-the-top glittery. (Too much disco dust can make your cake look like some little kid went crazy with the glitter if you're not careful.)
I just bought a Cricut machine and a snowflake template, so once UPS can get through the snow to deliver it I'll see what that can do and report back.