Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
Like the name suggests, this background image consists of a pattern of dark bricks. It may be an option for you, if you are looking for something that looks like a brick wall for use as a background on web pages. It's not a masterpiece, but looks pretty nice when is tiled.
Source V. Hartikainen
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
Dark pattern with some nice diagonal stitched lines crossing over.
Source Ashton
ZeroCC tileable moss texture, photographed and made by me. CC0
Source Sojan Janso
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From an image on opengameart.org shared by rubberduck.
Source Firkin
emixed from a JPG that was uploaded to Pixabay by Kyotime
Source Firkin
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Prismatic Groovy Concentric Background 5
Source GDJ
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
The original has been presented as black on transparent and stored in the pattern definitions. To retrieve the unit tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
From a drawing in 'Codogno e il suo territorio nella cronaca e nella storia'', Gio and Giarella Cairo, 1897.
Source Firkin
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
This metal background pattern resembles a metal plate with rivets. Solid rivets on a metal plate.
Source V. Hartikainen
I’m starting to think I have a concrete wall fetish.
Source Atle Mo