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
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Abstract Ellipses Background Grayscale
Source GDJ
Zero CC tileable dry grass texture, photographed and made by me. CC0
Source Sojan Janso
Prismatic Basic Pattern 2 No Background
Source GDJ
The following orange background pattern resembles a honeycomb.
Source V. Hartikainen
A seamless pattern formed from background pattern 102
Source Firkin
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Prismatic Groovy Concentric Background 2
Source GDJ
Classic 45-degree pattern, light version.
Source Luke McDonald
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
This light yellow background pattern consists of an irregular pattern of spots. Here's a light background pattern with yellowish tint.
Source V. Hartikainen
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
From a drawing in 'Codogno e il suo territorio nella cronaca e nella storia'', Gio and Giarella Cairo, 1897.
Source Firkin
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
Have you wondered about how it feels to be buried alive? Here is the pattern for it.
Source Hendrik Lammers
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba