An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
Wild Oliva or Oliva Wilde? Darker than the others, sort of a medium dark pattern.
Source Badhon Ebrahim
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
Subtle scratches on a light gray background.
Source Andrey Ovcharov
Original seamless pattern with an Inkscape filter.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Prismatic Basic Pattern 2 No Background
Source GDJ
Seamless Olive Green Web Background Image
Source V. Hartikainen
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
A seamless background of warped stripes on paper.
Source V. Hartikainen
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
From a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
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 ons is quite old school looking. Retro, even. I like it.
Source Arno Declercq
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
Abstract Tiled Background Extended 10
Source GDJ