People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Everyone needs some stardust. Sprinkle it on your next project.
Source Atle Mo
From drawing in 'Musings in Maoriland', Thomas Bracken, 1890.
Source Firkin
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Prismatic Floral Background No Black
Source GDJ
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Luxury pattern, looking like it came right out of Paris.
Source Daniel Beaton
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
The following orange background pattern resembles a honeycomb.
Source V. Hartikainen
A seamless textured paper for backgrounds. Colored in pale orange hues.
Source V. Hartikainen
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
Vector version of a JPG that was uploaded to Pixabay by theasad121
Source Firkin