A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Zero CC tileable brick texture, photographed and made by me. CC0
Source Sojan Janso
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
Prismatic Abstract Background Design No Black
Source GDJ
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
There are many carbon patterns, but this one is tiny.
Source Designova
I’m guessing this is related to the Sony Vaio? It’s a nice pattern no matter where it’s from.
Source Zigzain
This is a remix of "flower seamless pattern".I rotated the original image by 90 degrees.This is a seamless pattern of flowers.These horizontal wavy lines are one of Edo patterns which is called "tatewaku or tachiwaku or 立湧" that represents uprising steam or vapor.
Source Yamachem
A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.
Source Firkin
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
I love these crisp, tiny, super subtle patterns.
Source Badhon Ebrahim
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Prismatic Geometric Pattern Background No Black
Source GDJ
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Curved Diamond Pattern No Background
Source GDJ
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić