Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
The name alone is awesome, but so is this sweet dark pattern.
Source Federica Pelzel
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab