Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
Zero CC tileable seed texture, edited by me to be seamless from a Pixabay image. CC0
Source Sojan Janso
Colour version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
A seamless background texture of old cardboard.
Source V. Hartikainen
A free green background pattern with a pattern of rhombuses on a seamless texture. Feel free to use it as a tiled background image on your web site.
Source V. Hartikainen
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
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
An attempt for cleaning up the original image in a few steps.
Source Lazur URH
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
Looks like an old wall. I guess that’s it then?
Source Viahorizon
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett