Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Bumps, highlight and shadows – all good things.
Source Badhon Ebrahim
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Feel free to download this "Dark Wood" background texture for your web site. The background tiles seamlessly!
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
Prismatic Abstract Geometric Background 5
Source GDJ
Psychedelic Geometric Background No Black
Source GDJ
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen
A seamless pattern formed from a tile made from page ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Dark blue concrete wall with some small dust spots.
Source Atle Mo
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
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
Retro Circles Background 7 No Black
Source GDJ
A seamless background of warped stripes on paper.
Source V. Hartikainen
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
The tile can be had by selecting the rectangle in Inkscape and using shift+alt+i. Remixed from a drawing in 'Flowers of Song', Frederick Weatherly, 1895.
Source Firkin
Remixed from a JPG that was uploaded to Pixabay by Osckar
Source Firkin
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees