It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
Geometric triangles seem to be quite hot these days.
Source Pixeden
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
The image depicts a seamless pattern of pine tree leaves.
Source Yamachem
Prismatic Abstract Geometric Background derived from an image on Pixabay.
Source GDJ
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
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
We have some linen patterns here, but none that are stressed. Until now.
Source Jordan Pittman
All good things come in threes, so I give you the third in my little concrete wall series.
Source Atle Mo
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Tiny circle waves, almost like the ocean.
Source Sagive
Dark pattern with some nice diagonal stitched lines crossing over.
Source Ashton
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin