It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
From a drawing in 'A Rolling Stone. A tale of wrongs and revenge', John Hartley, 1878.
Source Firkin
A seamless pattern based on a tile that can be achieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A background pattern with a look of rough fabric.
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A free grid paper background pattern for using on web sites.
Source V. Hartikainen
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
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
You guessed it – looks a bit like cloth.
Source Peax Webdesign
This is a remix of "geometrical pattern 01".
Source Yamachem
Alternative colour scheme for the original floral pattern.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857
Source Firkin
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
The name is totally random, but hey, it sounds good.
Source Atle Mo
Prismatic Geometric Pattern Background 2
Source GDJ
Remixed from an image on Pixabay uploaded by Prawny
Source Firkin
A dark pattern made out of 3×3 circles and a 1px shadow. This works well as a carbon texture or background.
Source Atle Mo
Zero CC tileable brick texture, photographed and made by me. CC0
Source Sojan Janso