Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i
Source Firkin
I’m starting to think I have a concrete wall fetish.
Source Atle Mo
The following repeating website background is colored in a blue gray color and resembles a concrete wall or something similar to it.
Source V. Hartikainen
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Black brick wall pattern. Brick your site up!
Source Alex Parker
Coming in at 666x666px, this is an evil big pattern, but nice and soft at the same time.
Source Atle Mo
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Square design drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen
I guess this is inspired by the city of Ravenna in Italy and its stone walls.
Source Sentel
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers