Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
A free green background pattern with a pattern of rhombuses on a seamless texture. Feel free to use it as a tiled background image on your web site.
Source V. Hartikainen
Adapted from an image that was uploaded to Pixabay by Anerma.
Source Firkin
A seamless pattern of "sewn stripes" colored in light gray.
Source V. Hartikainen
ZeroCC tileable stone texture, edited from pixabay, CC0
Source Sojan Janso
Looks like an old wall. I guess that’s it then?
Source Viahorizon
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A seamless texture traced from an image on opengameart.org shared by Scouser.
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
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
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
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
A seamless textured paper for backgrounds. Colored in pale orange hues.
Source V. Hartikainen
Zero CC tileable Laminate wood texture, photographed and made by me. CC0
Source Sojan Janso
Submitted in a cream color, but you know how I like it.
Source Devin Holmes
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Hey, you never know when you’ll need a bird pattern, right?
Source Pete Fecteau