It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
Square design drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
8 by 8 pixels, and just what the title says.
Source pixilated
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
A re-make of the Gradient Squares pattern.
Source Dimitar Karaytchev
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
A seamless pattern formed from miutopia mug remixes on a tablecloth.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
An abstract pale yellow paper-like background with stains colored in yellow and green.
Source V. Hartikainen
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Might not be super subtle, but quite original in its form.
Source Alex Smith
Just the symbols of the signs of the zodiac distributed in a chequer board-like pattern
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Psychedelic Geometric Background No Black
Source GDJ
An alternative colour scheme for the original background.
Source Firkin
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This ladies and gentlemen, is texturetastic! Love it.
Source Adam Pickering
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin