An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
Here's a dark background pattern that contains a steel grid pattern as a texture. Use it as a website background or for other purposes. It's free!
Source V. Hartikainen
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Prismatic Polka Dots Mark II No Background
Source GDJ
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
Fake or not, it’s quite luxurious.
Source Factorio.us Collective
This beige background pattern resembles a concrete wall with engravings or something similar to it.
Source V. Hartikainen
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
Prismatic Abstract Geometric Background 5
Source GDJ
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Seamless Light Background Texture.
Source V. Hartikainen
Washi (和紙?) is a type of paper made in Japan. Here’s the pattern for you!
Source Carolynne
Small dots with minor circles spread across to form a nice mosaic.
Source John Burks
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
With a name like this, it has to be hot. Diagonal lines in light shades.
Source Isaac
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ
Imagine you zoomed in 1000X on some fabric. But then it turned out to be a skeleton!
Source Angelica
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin