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
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
A re-make of the Gradient Squares pattern.
Source Dimitar Karaytchev
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
A dark striped seamless pattern suitable for use as a background on websites.
Source V. Hartikainen
I asked Gjermund if he could make a pattern for us – result!
Source Gjermund Gustavsen
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
ZeroCC tileable mossy (lichen) stone texture, edited from pixabay. CC0
Source Sojan Janso
Lovely pattern with splattered vintage speckles.
Source David Pomfret
Black paper texture, based on two different images.
Source Atle Mo
Based from Design Kindle
Gold Triangular Seamless Pattern No Background
Source GDJ
The image is the remix of "wire-mesh fence seamless pattern" .This is a more minute version of it.Sorry for the file size.Using path>difference in Inkscape, I will cut out any silhouette from this pattern and create a "meshed silhouette".
Source Yamachem
Inspired by a drawing seen in 'City of Liverpool', James Picton, 1883.
Source Firkin
A grayscale fabric pattern with vertical lines of stitch holes.
Source V. Hartikainen
Super detailed 16×16 tile that forms a beautiful pattern of straws.
Source Pavel
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin