Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
The name alone is awesome, but so is this sweet dark pattern.
Source Federica Pelzel
Prismatic Geometric Pattern Background 2 No Black
Source GDJ
Zero CC tileable grass texture, photographed and made by me. CC0
Source Sojan Janso
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
The original has been presented as black on transparent and stored in the pattern definitions. To retrieve the unit tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Prismatic Geometric Tessellation Pattern 3 No Background
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Geometric Pattern Background 2
Source GDJ
A light brushed aluminum pattern for your pleasure.
Source Tim Ward
A seamless design of flowers remixed from a jpg on Pixabay by Prawny.
Source Firkin
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Actually remixed from a pattern on Pixabay. But then noticed a very similar one on Openclipart.org uploaded by btj51q2.
Source Firkin
Derived from a corner decoration itself found as a jpg on Pixabay.
Source Firkin
Geometric lines are always hot, and this pattern is no exception.
Source Listvetra
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
Prismatic Triangular Background Design Mark II 5
Source GDJ