Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
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
I love the movie Pineapple Express, and I’m also liking this Pineapple right here.
Source Audee Mirza
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Triangular Background Design Mark II 5
Source GDJ
Looks like an old wall. I guess that’s it then?
Source Viahorizon
Inspired by the B&O Play, I had to make this pattern.
Source Atle Mo
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
This is sort of fresh, but still feels a bit old school.
Source Martuchox
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
A seamless pattern formed from miutopia mug remixes on a tablecloth.
Source Firkin
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom