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
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
Prismatic Groovy Concentric Background
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
Sort of reminds me of those old house wallpapers.
Source Tish
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Abstract Geometric Background 3
Source GDJ
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
A background pattern with a look of rough fabric.
Source V. Hartikainen
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
Never out of fashion and so much hotter than the 45º everyone knows, here is a sweet 60º line pattern.
Source Atle Mo
Geometric lines are always hot, and this pattern is no exception.
Source Listvetra
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
ZeroCC tileable moss texture, photographed and made by me. CC0
Source Sojan Janso
Tiny little fibers making a soft and sweet look.
Source Badhon Ebrahim
Retro Circles Background 7 No Black
Source GDJ
A green background pattern with warped vertical stripes and a grunge look.
Source V. Hartikainen