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
Washi (和紙?) is a type of paper made in Japan. Here’s the pattern for you!
Source Carolynne
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
The name alone is awesome, but so is this sweet dark pattern.
Source Federica Pelzel
The file was named striped lens, but hey – Translucent Fibres works too.
Source Angelica
Pattern produced in Paint.net using the Vibrato plug-in.
Source Firkin
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
Background formed from the original with an emboss effect.
Source Firkin
A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A pale olive green background with a seamless texture.
Source V. Hartikainen
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
Black & white version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
Zero CC tileable hard cover cells book texture, 4k, scanned and made by me. CC0
Source Sojan Janso
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Zero CC plastic pattern texture, photographed and made by me. CC0 *Note, this texture was on the perfectly smooth surface of a plastic shovel scraper, not sure how to call it. Plz coment if you know what its called.
Source Sojan Janso