Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
If you want png files of thisu can download them here :
Source Viscious-Speed
A free seamless background pattern for use on websites.
Source V. Hartikainen
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
Based on an image that was uploaded to Pixabay by devanath
Source Firkin
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A seamless background pattern with impressed gray dots.
Source V. Hartikainen
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The classic notebook paper with horizontal stripes.
Source Are Sundnes
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
Number five from the same submitter, makes my job easy.
Source Dima Shiper
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin