A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
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
Tiny little fibers making a soft and sweet look.
Source Badhon Ebrahim
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Abstract Background Design
Source GDJ
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Prismatic Abstract Geometric Background 4
Source GDJ
Derived from a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
A seamless texture of a rough concrete surface.
Source V. Hartikainen