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
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
No idea what Nistri means, but it’s a crisp little pattern nonetheless.
Source Markus Reiter
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Geometric Pattern Background 2
Source GDJ
Seamless pattern formed from a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Background Wall, Art Abstract, Star Well & CC0 texture.
Source Ractapopulous
From a drawing in 'Prose and Verse ', William Linton, 1836.
Source Firkin
This one needs to be used in small areas; you can see it repeat.
Source Luca
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Adapted from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
Pattern produced in Paint.net using the Vibrato plug-in.
Source Firkin
Zero CC tileable hard cover green book, scanned and made by me. CC0
Source Sojan Janso
Remixed from a drawing in 'Очерки Русской Исторіи въ памятникахъ быта', Petr Polevoi, 1879.
Source Firkin