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
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
Prismatic Curved Diamond Pattern 2 No Background
Source GDJ
Black version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
A free tileable background colored in off-white (antique white) color.
Source V. Hartikainen
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
Colorful Floral Background 3 No Black
Source GDJ
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
Nicely executed tiling for an interesting pattern.
Source Ignasi Àvila Padró
A seamless background of warped stripes on paper.
Source V. Hartikainen
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A comeback for you: the popular Escheresque, now in black.
Source Patten
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
It’s like Shine Dotted’s sister, only rotated 45 degrees.
Source mediumidee
This background texture resembles stone. It may be used as a background on web pages or on some of their html elements (header, borders, menu bar, etc.). Just modify it for your needs.
Source V. Hartikainen
This is a seamless pattern which is derived from a flower petal image.
Source Yamachem
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The image depicts a Japanese Edo pattern called "kanoko or 鹿の子" meaning "fawn" which has a fur with small white spots.
Source Yamachem
From a drawing in 'Hyde Park from Domesday-Book to date', John Ashton, 1896.
Source Firkin