Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Here's an yet another seamless note paper texture for use as a background on websites.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Not the Rebel alliance, but a dark textured pattern.
Source Hendrik Lammers
This one is amazing, truly original. Go use it!
Source Viahorizon
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A seamless pattern formed from a square tile based on a jpg on Pixabay. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
A seamless pattern the starting point for which was a 'light rays' rendering in Paint.net.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Geometric Tessellation Pattern 3 No Background
Source GDJ
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
A seamless marble-like texture colored in light blue.
Source V. Hartikainen
Alternative colour scheme for the original floral pattern.
Source Firkin
Luxury pattern, looking like it came right out of Paris.
Source Daniel Beaton
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
The Grid. A digital frontier. I tried to picture clusters of information as they traveled through the computer.
Source Haris Šumić
The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Vertical lines with a bumpy, yet crisp, feel to it.
Source Raasa
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin