A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
A very slick dark rubber grip pattern, sort of like the grip on a camera.
Source Sinisha
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
You know I’m a sucker for these. Well-crafted paper pattern.
Source Mihaela Hinayon
This background pattern has futuristic look. So, maybe it could be used on websites or blogs dedicated to video games?!
Source V. Hartikainen
Tiny little fibers making a soft and sweet look.
Source Badhon Ebrahim
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
From a drawing in 'Codogno e il suo territorio nella cronaca e nella storia'', Gio and Giarella Cairo, 1897.
Source Firkin
Number 4 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
Inspired by a pattern found in 'A General History of Hampshire, or the County of Southampton, including the Isle of Wight', Bernard Woodwood, 1861
Source Firkin
A dark striped seamless pattern suitable for use as a background on websites.
Source V. Hartikainen
Number 5 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
This light blue background pattern is quite pleasing to the eye, it consists of a tiny rough grid pattern, which is seamless by design. That's it, if you like the color, you can use this seamless pattern in a web design without making any further modifications to it.
Source V. Hartikainen
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin