The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
Feel free to download and use it, or see the rest of the dark background patterns that I have made. Anyway, I hope you will find something that you like.
Source V. Hartikainen
A repeating background of thick textured paper. Actually, it turned out to look like something between a paper and fabric.
Source V. Hartikainen
A seamless pattern formed from a tile made from page ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A blue background wallpaper for websites. It has a seamless texture with vertical stripes. It looks quite nice not only when using as a tiled background on websites, but also on computer desktops.
Source V. Hartikainen
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
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
From an image on opengameart.org shared by rubberduck.
Source Firkin
Fix and cc0 to get the tile this is based on.
Source SliverKnight
Vertical lines with a bumpy, yet crisp, feel to it.
Source Raasa
A web texture of brown canvas. Will look great, when used in dark web designs.
Source V. Hartikainen
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
On a large canvas you can see it tiling, but used on smaller areas, it’s beautiful.
Source Paul Phönixweiß