Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
Tiny circle waves, almost like the ocean.
Source Sagive
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Zero CC tileable ground cracked, crackled, texture, made by me.
Source Sojan Janso
Psychedelic Geometric Background No Black
Source GDJ
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin