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
Fabric-ish patterns are close to my heart. French Stucco to the rescue.
Source Christopher Buecheler
Washi (和紙?) is a type of paper made in Japan. Here’s the pattern for you!
Source Carolynne
Retro Circles Background 7 No Black
Source GDJ
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
This is the remix of "blue wave-seigaiha".The image depicts a seamless pattern of the front upper part of Japanese five yen coin which is used currently.This design represents a rice with ripe golden ears.
Source Yamachem
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Super detailed 16×16 tile that forms a beautiful pattern of straws.
Source Pavel
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
Remixed from a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Derived from a corner decoration itself found as a jpg on Pixabay.
Source Firkin
Thin lines, noise and texture creates this crisp dark denim pattern.
Source Marco Slooten
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Prismatic Abstract Geometric Background 3
Source GDJ