A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
This background image has seamless texture that resembles a surface of gray stone.
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
Prismatic Groovy Concentric Background No Black
Source GDJ
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin