Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
A bit like some carbon, or knitted netting if you will.
Source Anna Litvinuk
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Hey, you never know when you’ll need a bird pattern, right?
Source Pete Fecteau
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
A rusty grunge background for websites. Feel free to use it in your site's theme.
Source V. Hartikainen
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Utilising a bird from s-light and some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Redrawn based on a drawing in 'По Сѣверо-Западу Россіи' Konstantin Sluchevsky, 1897.
Source Firkin
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
Psychedelic Geometric Background No Black
Source GDJ
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
This is a semi-dark pattern, sort of linen-y.
Source Sagive SEO
Classic vertical lines, in all its subtlety.
Source Cody L