Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
This was formed by distorting an image of a background on Pixabay.
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
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Prismatic Abstract Line Art Pattern Background
Source GDJ
I love cream! 50x50px and lovely in all the good ways.
Source Thomas Myrman
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
A pale orange background pattern with glossy groove stripes.
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
The image is a design of blue glass.How about using it as background image?
Source Yamachem
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
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
Found on the ground in french cafe in kunming, Yunnan, china
Source Rejon
The image depicts a seamless pattern of a snow crystal.I referred to a book called ”sekka-zusetsu” or "雪華図説" which means an illustrated explanation about snow crystals.This book was published in 1832 (天保3年) or Edo period.For more about "雪華図説",see here:dl.ndl.go.jp/info:ndljp/pid/2536975
Source Yamachem
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Continuing the geometric trend, here is one more.
Source Mike Warner
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin