A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Zero CC tileable hard cover cells, skin like, book texture. 4K, Scanned and made by me CC0
Source Sojan Janso
There are many carbon patterns, but this one is tiny.
Source Designova
Light and tiny, just the way you like it.
Source Rohit Arun Rao
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
The image depicts a seamless pattern of a tortoise in tortoiseshell (hexagon).
Source Yamachem
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
Prismatic Abstract Geometric Background 5
Source GDJ
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
Washi (和紙?) is a type of paper made in Japan. Here’s the pattern for you!
Source Carolynne