Thin lines, noise and texture creates this crisp dark denim pattern.
Source Marco Slooten
It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
A light gray fabric pattern with faded vertical stripes.
Source V. Hartikainen
Prismatic 3D Isometric Tessellation Pattern 6
Source GDJ
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
Prismatic Polka Dots 3 No Background
Source GDJ
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Abstract Geometric Background 5
Source GDJ
Retro Circles Background 4 No Black
Source GDJ
Prismatic Chevrons Pattern 5 With Background
Source GDJ
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin