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 seamless pattern drawn originally in Paint.net by distorting a slice of background pattern 116 and copying the resulting triangle numerous times.
Source Firkin
Remixed from a raster on Pixabay, that was uploaded by ArtsyBee.
Source Firkin
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
Tweed is back in style – you heard it here first. Also, the @2X version here is great!
Source Simon Leo
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Prismatic Geometric Tessellation Pattern 3 No Background
Source GDJ
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
A repeating background with dark brown stone-like texture and abstract pattern that looks like tree trunks.
Source V. Hartikainen
A seamless background colored in pale orange. It has a paper like texture with diagonal grid pattern.
Source V. Hartikainen
From a drawing in 'From Snowdon to the Sea. Striking stories of North and South Wales', Marie Trevelyan, 1895.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
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