A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
Remixed from an image that was uploaded to Pixabay by KirstenStar
Source Firkin
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A bit simplified version. Although it could be edited out to be simpler. Anyway, this time the tiling is converted to a pattern fill -which is using clipping for the tile's edges.
Source Lazur URH
This one has rusty dark brown texture.
Source V. Hartikainen
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
Everyone needs some stardust. Sprinkle it on your next project.
Source Atle Mo
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Very simple, very blu(e). Subtle and nice.
Source Seb Jachec
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
Here's an yet another background for websites, with a seamless texture of wood planks this time.
Source V. Hartikainen
White little knobs, coming in at 10x10px. Sweet!
Source Amos
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
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin