I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A free seamless background image with abstract texture of green "curtain".
Source V. Hartikainen
The following orange background pattern resembles a honeycomb.
Source V. Hartikainen
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
A fun-looking elastoplast/band-aid pattern. A hint of orange tone in this one.
Source Josh Green
Small dots with minor circles spread across to form a nice mosaic.
Source John Burks
A seamless texture traced from an image on opengameart.org shared by Scouser.
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
A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
A seamlessly tileable pink background texture.
Source V. Hartikainen
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
By popular request, an outline version of the pentagon pattern.
Source Atle Mo
The base gradient edited so now more details are rendered.
Source Lazur URH
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This is a grid, only it’s noisy. You know. Reminds you of those printed grids you draw on.
Source Vectorpile
More Japanese-inspired patterns, Gold Scales this time.
Source Josh Green
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
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
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Looks like an old wall. I guess that’s it then?
Source Viahorizon