A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
Almost like little fish shells, or dragon skin.
Source Graphiste
The classic notebook paper with horizontal stripes.
Source Are Sundnes
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
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
To celebrate the new feature, we need some sparkling diamonds.
Source Atle Mo
So tiny, just 7 by 7 pixels – but still so sexy. Ah yes.
Source Dmitriy Prodchenko
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
A seamless pattern of "sewn stripes" colored in light gray.
Source V. Hartikainen
I scanned a paper coffee cup. You know, in case you need it.
Source Atle Mo
Prismatic Geometric Pattern Background
Source GDJ
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran