Made these a few years ago using public domain photographs of snowflakes. They were originally created in Photoshop CS2, so they should work with CS3; I know they work with CS4 because I tested them myself! Whether or not they'll work with earlier versions of Photoshop remains to be seen./update:
Added the PNG images I used to make these brushes. If the abr file doesn't work with your version of Photoshop, or you don't have Photoshop, then you can use these images to create brushes for your program.
Enjoy! And Happy Holidays