The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
Prismatic Hexagonalism Pattern No Background
Source GDJ
Inspired by a drawing seen in 'City of Liverpool', James Picton, 1883.
Source Firkin
This background pattern contains a seamless texture of bark. It's not very realistic, but I think it looks quite nice.
Source V. Hartikainen
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
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
Here's a tile-able wood background image for use in web design.
Source V. Hartikainen
Zero CC tileable hard cover red book, scanned and made by me. CC0
Source Sojan Janso
Prismatic Curved Diamond Pattern No Background
Source GDJ
Light gray paper pattern with small traces of fiber and some dust.
Source Atle Mo
Prismatic Geometric Pattern Background
Source GDJ
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
Here's an yet another background for websites, with a seamless texture of wood planks this time.
Source V. Hartikainen
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Seamless Dark Grunge Texture. Here's a new grunge texture for use as a background.
Source V. Hartikainen
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin
Prismatic Geometric Pattern Background No Black
Source GDJ
Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A pale yellow background pattern with vertical stripes. The stripes are partially faded. I think this background image turned out pretty well, especially those faded stripes.
Source V. Hartikainen