The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
An orange vertically striped background pattern. Feel free to download and use this orange background pattern, for example, on the web). It resembles a wallpaper with vertical stripes or something similar to it.
Source V. Hartikainen
I guess this is inspired by the city of Ravenna in Italy and its stone walls.
Source Sentel
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
A re-make of the Gradient Squares pattern.
Source Dimitar Karaytchev
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
Formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
Here's an yet another seamless note paper texture for use as a background on websites.
Source V. Hartikainen
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
Prismatic Abstract Geometric Background 2 No Black
Source GDJ