It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Seamless pattern inspired by a drawing on Pixabay. To get the tile this is formed from, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
An attempt for cleaning up the original image in a few steps.
Source Lazur URH
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
If you’re sick of the fancy 3D, grunge and noisy patterns, take a look at this flat 2D brick wall.
Source Listvetra
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
Zero CC tileable wood texture, made by me procedurally in Neo Texture Edit.
Source Sojan Janso
Derived from an image that was uploaded to Pixabay by darkmoon1968
Source Firkin
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless texture of black leather. I think it will look best when used in headers, footers or sidebars.
Source V. Hartikainen