Embossed lines and squares with subtle highlights.
Source Alex Parker
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
From a drawing in 'A Life Interest', Mrs Alexander, 1888.
Source Firkin
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
A bit of scratched up grayness. Always good.
Source Dmitry
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
An abstract texture of black metal pipes (seamless).
Source V. Hartikainen
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
The name is totally random, but hey, it sounds good.
Source Atle Mo
Seamless Prismatic Quadrilateral Line Art Pattern No Background
Source GDJ
A version without colours blended together to give a different look.
Source Firkin
A frame using leaves from an image that was uploaded to Pixabay by mayapujiati
Source Firkin
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Colour version of the original pattern.
Source Firkin