People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Looks like an old wall. I guess that’s it then?
Source Viahorizon
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Honestly, who does not like a little pipe and mustache?
Source Luca Errico
A seamless background pattern with impressed gray dots.
Source V. Hartikainen
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
Background Wall, Art Abstract, white Well & CC0 texture.
Source Ractapopulous
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
On a large canvas you can see it tiling, but used on smaller areas, it’s beautiful.
Source Paul Phönixweiß
An attempt for cleaning up the original image in a few steps.
Source Lazur URH
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Prismatic Hexagonalist Pattern No Background
Source GDJ
Hey, you never know when you’ll need a bird pattern, right?
Source Pete Fecteau
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
The starting point for this was drawn on the web site steamcoded.org/PolyskelionMaker.svg
Source Firkin