Heads up, cool kids: Math is way hip. Particularly, geometry, facets, and gem shapes have been everywhere designy for the last two years, and there's no reason the holidays shouldn't be included in the trend.
Case in point: this geometric garland. It looks nice and handmade, is holiday-neutral, and the colors are winter-y enough that you could leave it up through February.
The folks at Blow Up! provide the whole how-to, including a free downloadable template that you can print off at will and make these things by the dozens. You could even make a few extra, add a loop of string, and turn them into some contemporary tree ornaments.
Chilly Geometric Garland [Urban Outfitters]