This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
An abstract Background pattern of purple twisty patterns.
Source TikiGiki
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
Derived from an image that was uploaded to Pixabay by starchim01
Source Firkin
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A comeback for you: the popular Escheresque, now in black.
Source Patten
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
Prismatic Hexagonalist Pattern No Background
Source GDJ
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
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
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
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
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green