A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
There are many carbon patterns, but this one is tiny.
Source Designova
A nice and simple white rotated tile pattern.
Source Another One
Prismatic Abstract Background Design No Black
Source GDJ
An alternative colour scheme to the original seamless pattern.
Source Firkin
Square design drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
This is a hot one. Small, sharp and unique.
Source GraphicsWall
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
You were craving more leather, so I whipped this up by scanning a leather jacket.
Source Atle Mo
Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Prismatic Polka Dots Mark II 2 No Background
Source GDJ
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Polka Dots Mark II 3 No Background
Source GDJ
Formed by distorting an image on Pixabay that was uploaded by gustavorezende. To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin