This crystal was captured 21 march 2013. I decided to process some more snowflakes from last winter's archive. In center of this crystal can be seen colored areas, caused by thin film optical interference effect (thanks to Don Komarechka!). Sometimes i saw similar colors in other crystals, but often these colors too subtle. I amplify it by averaging 16 serial shots (this removes most of color noise and makes coloured areas better defined), and enchance colors in LAB space (applied identical S-curves at channels A and B). Looks better in original resolution: 1059 x 794 pixels.
If you want to see more snowflakes, you can browse through all snowflake pictures.
Here you'll find snowflake photo wallpapers in numerous resolutions and screen proportions, up to Ultra HD 4K.
And here is article about snowflake macro photography.