A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
Prismatic Groovy Concentric Background 5 No Black
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
More in the paper realm, this time with fibers.
Source Jorge Fuentes
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
This is a grid, only it’s noisy. You know. Reminds you of those printed grids you draw on.
Source Vectorpile
A new take on the black linen pattern. Softer this time.
Source Atle Mo
Old China with a modern twist, take two.
Source Adam Charlts
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
The starting point for this was drawn on the web site steamcoded.org/PolyskelionMaker.svg
Source Firkin
Prismatic Triangular Background Design Mark II 5
Source GDJ
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless tessellation pattern. To get the tile this is formed from, select the pattern in Inkscape and use shift+alt+i.
Source Firkin
Remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Non-seamless pattern drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ