A free repetitive background with a dark concrete wall like texture. This one may be used in dark web site designs.
Source V. Hartikainen
Prismatic Polka Dots Mark II 2 No Background
Source GDJ
A nice looking light gray background pattern with diagonal stripes.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
From a drawing in 'A Life Interest', Mrs Alexander, 1888.
Source Firkin
Prismatic Triangular Background Design Mark II 5
Source GDJ
Submitted as a black pattern, I made it light and a few steps more subtle.
Source Andy
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
Background pattern originally a PNG drawn in Paint.net
Source Firkin
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Inspired by a 1930s wallpaper pattern I saw on TV.
Source Firkin
Derived from a JPG that was uploaded to Pixabay by ractapopulous
Source Firkin
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
Abstract Tiled Background Extended 8
Source GDJ
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
Fabric-ish patterns are close to my heart. French Stucco to the rescue.
Source Christopher Buecheler
This beige background pattern resembles a concrete wall with engravings or something similar to it.
Source V. Hartikainen
Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin