The image depicts a Japanese Edo pattern called "kanoko or 鹿の子" meaning "fawn" which has a fur with small white spots.
Source Yamachem
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
The rectangular 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
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
Classic 45-degree pattern, light version.
Source Luke McDonald
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Background Wall, Art Abstract, Star Well & CC0 texture.
Source Ractapopulous
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
A grayscale fabric pattern with vertical lines of stitch holes.
Source V. Hartikainen
The image depicts polka dot seamless pattern.
Source Yamachem
A dark metal plate with an embossed grid pattern and a bit of rust. Here's a dark metal plate texture for use as a tiled background on web pages.
Source V. Hartikainen
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
From an image on opengameart.org shared by rubberduck.
Source Firkin