To get the repeating unit, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen
This beige background pattern resembles a concrete wall with engravings or something similar to it.
Source V. Hartikainen
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
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
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
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
This is a grid, only it’s noisy. You know. Reminds you of those printed grids you draw on.
Source Vectorpile
A free seamless texture of reptile skin colored in a dark brown color. As always, you may use it as a repeated background image in your web design works, or for any other purposes.
Source V. Hartikainen
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
A background pattern with wavy green vertical stripes. This one has green stripes on a white background. Download if you like it.
Source V. Hartikainen
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
The file was named striped lens, but hey – Translucent Fibres works too.
Source Angelica