This was formed by distorting an image of a background on Pixabay.
Source Firkin
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Remixed from a JPG that was uploaded to Pixabay by theasad121
Source Firkin
Prismatic Groovy Concentric Background 3
Source GDJ
Black brick wall pattern. Brick your site up!
Source Alex Parker
CC0 and seamless wellington boot pattern.
Source SliverKnight
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Smooth Polaroid pattern with a light blue tint.
Source Daniel Beaton
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Honestly, who does not like a little pipe and mustache?
Source Luca Errico
The image a seamless pattern of a wire-mesh fence.I want you to use this pattern as a lower layer.
Source Yamachem
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
ZeroCC tileable moss texture, photographed and made by me. CC0
Source Sojan Janso
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin