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
A free seamless background pattern for use on websites.
Source V. Hartikainen
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
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
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Just like your old suit, all striped and smooth.
Source Alex Berkowitz
This one is quite simple in design, it consists of vertical stripes layered on top of a seamless texture.
Source V. Hartikainen
Prismatic Groovy Concentric Background 5 No Black
Source GDJ
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Zero CC asphalt, pavement, texture, photographed and made by me. CC0 WARNING I FOUND A SEAM ON THIS TEXTURE
Source Sojan Janso
Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
Mostly just mucked about with the colours and made one of the paths in the lead frame opaque. The glass remains transparent.
Source Firkin
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso