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 following orange background pattern resembles a honeycomb.
Source V. Hartikainen
Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Number 3 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Zero CC tileable wood texture, made by me procedurally in Neo Texture Edit.
Source Sojan Janso
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Bond Slaves. The story of a struggle.', Isabella Varley, 1893.
Source Firkin
Uses spirals from Pixabay. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Kaleidoscope Prismatic Abstract No Background
Source GDJ
Remixed from a drawing that was uploaded to Pixabay by DavidZydd
Source Firkin
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Remixed from a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
Here's a quite bright pink background pattern for use on websites. It doesn't look like a real fur, but it definitely resembles one.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Just the symbols of the signs of the zodiac distributed in a chequer board-like pattern
Source Firkin
A seamless background pattern with impressed gray dots.
Source V. Hartikainen
Prismatic Abstract Line Art Pattern Background
Source GDJ
Zero CC tileable ground cracked, crackled, texture, made by me.
Source Sojan Janso
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
A new one called white wall, not by me this time.
Source Yuji Honzawa