Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Subtle scratches on a light gray background.
Source Andrey Ovcharov
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Black paper texture, based on two different images.
Source Atle Mo
Based from Design Kindle
Seamless Background For Websites. It has a texture similar to cork-board.
Source V. Hartikainen
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
White circles connecting on a light gray background.
Source Mark Collins
Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
The following repeating website background is colored in a blue gray color and resembles a concrete wall or something similar to it.
Source V. Hartikainen
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin