This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
A dark metallic background with a pattern of stamped dots. Here's a dark "metallic" background pattern for you.
Source V. Hartikainen
A seamless striped fabric-like texture colored in a dark reddish brown color.
Source V. Hartikainen
The original enhanced with some gradients.
Source Firkin
A rusty grunge background for websites. Feel free to use it in your site's theme.
Source V. Hartikainen
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Lovely light gray floral motif with some subtle shades.
Source GraphicsWall
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Remixed from a drawing in 'Line and form", Walter Crane, 1914.
Source Firkin