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 grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
From a drawing in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
Derived from a corner decoration itself found as a jpg on Pixabay.
Source Firkin
Looks like an old wall. I guess that’s it then?
Source Viahorizon
Nothing like a clean set of bed sheets, huh?
Source Badhon Ebrahim
From a design in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
A bit like some carbon, or knitted netting if you will.
Source Anna Litvinuk
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
This is the remix of an OCAL clipart called "Rain on Window" uploaded by "pagarmidna".Thanks.This is a seamless pattern of raindrops.
Source Yamachem
I’m not going to use the word Retina for all the new patterns, but it just felt right for this one. Huge wood pattern for ya’ll.
Source Atle Mo
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts