From a drawing in 'Cassell's Library of English Literature', Henry Morley, 1883.
Source Firkin
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
Lovely pattern with some good-looking non-random noise lines.
Source Zucx
Prismatic Curved Diamond Pattern 4 No Background
Source GDJ
The name tells you it has curves. Oh yes, it does!
Source Peter Chon
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
Zero CC tileable bark texture, 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
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Have you wondered about how it feels to be buried alive? Here is the pattern for it.
Source Hendrik Lammers
Colourful background achieved with gradient fills.
Source Firkin
A bit of scratched up grayness. Always good.
Source Dmitry
Prismatic Polka Dots Mark II No Background
Source GDJ
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin