The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
A version without colours blended together to give a different look.
Source Firkin
A seamless stone-like background for blogs or any other type of websites.
Source V. Hartikainen
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Prismatic Abstract Background Design
Source GDJ
Has nothing to do with toast, but it’s nice and subtle.
Source Pippin Lee
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i
Source Firkin
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Like the name suggests, this background image consists of a pattern of dark bricks. It may be an option for you, if you are looking for something that looks like a brick wall for use as a background on web pages. It's not a masterpiece, but looks pretty nice when is tiled.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Polka Dots 3 No Background
Source GDJ
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
Not so subtle. These tileable wood patterns are very useful.
Source Elemis
A pattern drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
No, not the band but the pattern. Simple squares in gray tones, of course.
Source Atle Mo
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Remixed from a drawing in 'An Index to Deering's Nottinghamia Vetus et Nova', Rupert Chicken, 1899. The unit tile can be had by selecting the rectangle in Inkscape and using shift-alt-i
Source Firkin
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
This is the third pattern called Dark Denim, but hey, we all love them!
Source Brandon Jacoby
Luxurious looking pattern (for a T-shirt maybe?) with a hint of green.
Source Simon Meek