This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
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
I skipped number 3, because it wasn’t all that great. Sorry.
Source Dima Shiper
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
A bit like some carbon, or knitted netting if you will.
Source Anna Litvinuk
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Abstract Ellipses Background Grayscale
Source GDJ
A free grid paper background pattern for using on web sites.
Source V. Hartikainen
Colour version of the original pattern.
Source Firkin
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev