Subtle scratches on a light gray background.
Source Andrey Ovcharov
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 Groovy Concentric Background No Black
Source GDJ
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Geometric Pattern Background 2
Source GDJ
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Could be paper, could be a Polaroid frame – up to you!
Source Chaos
Derived from a JPG that was uploaded to Pixabay by ractapopulous
Source Firkin
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
Black version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
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
Floral patterns might not be the hottest thing right now, but you never know when you need it!
Source Lauren
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Remixed from an image on Pixabay, the original having been uploaded by darkmoon1968.
Source Firkin
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
The image is a design of blue glass.How about using it as background image?
Source Yamachem
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
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
Everyone needs some stardust. Sprinkle it on your next project.
Source Atle Mo
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers