An attempt for cleaning up the original image in a few steps.
Source Lazur URH
This was formed by distorting an image of a background on Pixabay.
Source Firkin
The image depicts a seamless pattern of a Japanese family crest called "chidori" in Japanese .A chidori in Japanese means a plover in English.
Source Yamachem
A fun-looking elastoplast/band-aid pattern. A hint of orange tone in this one.
Source Josh Green
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
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Traced from a drawing in 'Household Stories from the Collection of the Brothers Grimm', Wilhelm Carl Grimm , 1882.
Source Firkin
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
The tile for this is based on a repeating unit close to a design on Pixabay. It can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
Prismatic Snowflakes Pattern 3 No Background
Source GDJ
Black brick wall pattern. Brick your site up!
Source Alex Parker
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
Seamless Green Tile Background
Source V. Hartikainen
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin