Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
From a drawing in 'Less Black than we're painted', James Payn, 1884.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Wasn't satisfied with the original's colouring. Too much component transfer and colormatrixes yet the results are lacking a bit. So this time it is a simple black to transparent fade, making it possible remixing easily once there will be other blending modes supported as well. Probably in inkscape 0.92.
Source Lazur URH
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
Prismatic Snowflakes Pattern 2 No Background
Source GDJ
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
From a drawing of the coat of arms of the Ottoman Empire on Wikimedia.
Source Firkin
Zero CC tileable ground (#2) cracked, crackled texture, made by me. CC0
Source Sojan Janso
Prismatic Hexagonalism Pattern No Background
Source GDJ
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
A repeating background with wood/straw like texture.
Source V. Hartikainen
A seamless pattern recreated from an image on Pixabay. It is reminiscent of parquet flooring and is formed from a square tile, which can be recovered in Inkscape by selecting the ungrouped rectangle and using shift-alt-I together.
Source Firkin
A seamless pattern with green and yellow diagonal lines on top of a white dotted background.
Source V. Hartikainen
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Heavily remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount