An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Same classic 45-degree pattern, dark version.
Source Luke McDonald
A dark striped seamless pattern suitable for use as a background on websites.
Source V. Hartikainen
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Alternative colour scheme for the original floral pattern.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
Number 5 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
Prismatic Chevrons Pattern 5 With Background
Source GDJ