This one is amazing, truly original. Go use it!
Source Viahorizon
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
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I. A version of the original with random colors.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
Prismatic Triangular Background Design Mark II 5
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A bit of scratched up grayness. Always good.
Source Dmitry
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
From an image on opengameart.org shared by rubberduck.
Source Firkin
This is the remix of an OCAL clipart called "Art Nouveau ornament" uploaded by "microcosme".Thanks.This is a seamless pattern of an Art Nouveau ornament.
Source Yamachem
A nice one indeed, but I have a feeling we have it already? If you spot a copy, let me know on Twitter.
Source Graphiste
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Derived from an image that was uploaded to Pixabay by TheDigitalArtist
Source Firkin
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
A seamless pattern drawn originally in Paint.net by distorting a slice of background pattern 116 and copying the resulting triangle numerous times.
Source Firkin
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Retro Circles Background 4 No Black
Source GDJ
This background pattern contains worn out colorful stripes as a texture.
Source V. Hartikainen