Colour version that is close to the original drawing uploaded to Pixabay by pencilparker.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Prismatic Polka Dots Mark II 3 No Background
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
Background Wall, Art Abstract, Watercolor Vintage style CC0 texture.
Source Ractapopulous
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Produced using the clouds, flames and glass blocks plug-ins in Paint.net and the resulting .PNG vectorised with Vector Magic.
Source Firkin
Might not be super subtle, but quite original in its form.
Source Alex Smith
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
A seamless pattern formed from a modified version of rwwgub's tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
A version without colours blended together to give a different look.
Source Firkin
Free tiled background with colorful stripes and white splatter.
Source V. Hartikainen
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Feel free to use this seamless background texture as a background on a web site. It's colored in a light pink color and is seamlessly tile-able.
Source V. Hartikainen