A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Sharp pixel pattern, just like the good old days.
Source Paridhi
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Groovy Concentric Background 3
Source GDJ
Pattern formed from simple shapes. Black version.
Source Firkin
From a drawing in 'Hundert Jahre in Wort und Bild', S. Stefan, 1899.
Source Firkin
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
A nice and simple white rotated tile pattern.
Source Another One
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Not the Rebel alliance, but a dark textured pattern.
Source Hendrik Lammers
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
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