These are models of snowflakes that actually existed!  They are directly based off of some of Wilson A. Bentley's 1900's snowflake photographs which can be found here:
http://www.snowflakebentley.com/
https://siarchives.si.edu/sites/default/files/pdfs/WAB_Snow_1902.pdf

These models do really nicely with a filament change. Most of the models use a transition of 1 mm height. Images shown are a clear/translucent PLA to a multi-color Silk PLA.

A zip file of all ten snowflake STLs is available for download as well as the Solidworks model for each ten models.