CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
A seamless texture of a rough concrete surface.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Here's a seamless brown cork board background texture. Feel free to download or reshare if you like.
Source V. Hartikainen
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
Uses spirals from Pixabay. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.
Source Firkin
A fun-looking elastoplast/band-aid pattern. A hint of orange tone in this one.
Source Josh Green
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
A white version of the very popular linen pattern.
Source Ant Ekşiler
New paper pattern with a slightly organic feel to it, using some thin threads.
Source Atle Mo
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
This light background pattern has a texture of "frozen" surface with diagonal stripes. Here's an yet another addition to the collection of free website backgrounds.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Snowflakes Pattern No Background
Source GDJ
Background pattern originally a PNG drawn in Paint.net
Source Firkin
A free background pattern with abstract green tiles.
Source V. Hartikainen