It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Prismatic Rounded Squares Grid 3 No Background
Source GDJ
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A seamless background tile of aged paper with shabby look.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
The image depicts a seamless pattern of a Japanese family crest called "chidori" in Japanese .A chidori in Japanese means a plover in English.
Source Yamachem
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
Awesome name, great pattern. Who does not love space?
Source Nick Batchelor
A new take on the black linen pattern. Softer this time.
Source Atle Mo
Scanned some rice paper and tiled it up for you. Enjoy.
Source Atle Mo
Prismatic Hexagonalist Pattern No Background
Source GDJ
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
The file was named striped lens, but hey – Translucent Fibres works too.
Source Angelica
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
A seamless pattern formed from miutopia's cakes on a tablecloth.
Source Firkin
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Zero CC tileable moss or lichen covered stone texture, edited from pixabay. CC0
Source Sojan Janso
Square design drawn in Paint.net and vectorized in Vector Magic.
Source Firkin