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 original enhanced with some gradients.
Source Firkin
Prismatic Groovy Concentric Background 5
Source GDJ
Here's a tile-able wood background image for use in web design.
Source V. Hartikainen
To get the tile this is formed from 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
Remixed from a JPG that was uploaded to Pixabay by Osckar
Source Firkin
Square design drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
The perfect pattern for all your blogs about type, or type-related matters.
Source Atle Mo
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
A free repetitive background with a dark concrete wall like texture. This one may be used in dark web site designs.
Source V. Hartikainen
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
Dark pattern with some nice diagonal stitched lines crossing over.
Source Ashton
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Someone was asking about how to achieve a fur pattern at #inkscape irc so tried to make a filter on it. Flood filled fractal noises rigged together. May someone find a good use for these.
Source Lazur URH
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
A seamless texture of a rough concrete surface.
Source V. Hartikainen
More in the paper realm, this time with fibers.
Source Jorge Fuentes