Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!
Source Dertig Media
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
Looks like an old wall. I guess that’s it then?
Source Viahorizon
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
All good things come in threes, so I give you the third in my little concrete wall series.
Source Atle Mo
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
Sounds like something from World of Warcraft. Has to be good.
Source Tony Kinard
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
A bit of scratched up grayness. Always good.
Source Dmitry
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
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Inspired by a pattern found in 'A General History of Hampshire, or the County of Southampton, including the Isle of Wight', Bernard Woodwood, 1861
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
A seamless pattern formed from a modified version of rwwgub's tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Background Wall, Art Abstract, white Well & CC0 texture.
Source Ractapopulous
Prismatic Chevrons Pattern 5 With Background
Source GDJ
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin