A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
Just like your old suit, all striped and smooth.
Source Alex Berkowitz
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
I love cream! 50x50px and lovely in all the good ways.
Source Thomas Myrman
Alternative colour scheme. 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
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
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
Light and tiny, just the way you like it.
Source Rohit Arun Rao
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Sometimes you just need the simplest thing.
Source Fabricio
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Nasty or not, it’s a nice pattern that tiles. Like they all do.
Source Badhon Ebrahim
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
The image depicts a seamless pattern of the design which includes a stylized lotus and a stylized crane.I referred to the original image in a book which is into public domain.
Source Yamachem
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
Remixed from a drawing in 'Canadian forest industries July-December', 1915
Source Firkin
A classic dark tile for a bit of vintage darkness.
Source Listvetra
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO