A seamless pattern the starting point for which was a 'light rays' rendering in Paint.net.
Source Firkin
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Prismatic Groovy Concentric Background No Black
Source GDJ
Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
A free pink background pattern.
Source V. Hartikainen
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
The name alone is awesome, but so is this sweet dark pattern.
Source Federica Pelzel
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
Very simple, very blu(e). Subtle and nice.
Source Seb Jachec
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Paper model of a tetrahedron. Modelo de papel de um tetraedro.
Source laobc
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
Formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Might not be super subtle, but quite original in its form.
Source Alex Smith
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Remixed from a raster on Pixabay, that was uploaded by ArtsyBee.
Source Firkin