It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
A beautiful dark wood pattern, superbly tiled.
Source Omar Alvarado
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
Tiny circle waves, almost like the ocean.
Source Sagive
A free seamless background texture of "timber wall" (colored in dark brown).
Source V. Hartikainen
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
One more sharp little tile for you. Subtle circles this time.
Source Blunia
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Prismatic Abstract Geometric Background 4
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
A background pattern with wavy green vertical stripes. This one has green stripes on a white background. Download if you like it.
Source V. Hartikainen
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
A bit strange this one, but nice at the same time.
Source Diogo Silva
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Remixed from an image on Pixabay, the original having been uploaded by darkmoon1968.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
Remixed from a vector adapted from a jpg on Pixabay. The tile this is constructed from can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
From a drawing in 'Friend or Fortune? The story of a strange year', Robert Overton, 1897.
Source Firkin
You may use it as is, or modify it as you like.
Source V. Hartikainen
From a drawing in 'Bond Slaves. The story of a struggle.', Isabella Varley, 1893.
Source Firkin