A bit simplified version. Although it could be edited out to be simpler. Anyway, this time the tiling is converted to a pattern fill -which is using clipping for the tile's edges.
Source Lazur URH
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
This was formed by distorting an image of a background on Pixabay.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Colour version of the original pattern inspired by the front cover of 'Old and New Paris', Henry Edwards, 1894.
Source Firkin
Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!
Source Dertig Media
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
A beautiful dark wood pattern, superbly tiled.
Source Omar Alvarado
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
One more sharp little tile for you. Subtle circles this time.
Source Blunia
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
Prismatic Geometric Pattern Background No Black
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A seamless tessellation pattern. To get the tile this is formed from, select the pattern in Inkscape and use shift+alt+i.
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
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Prismatic Abstract Geometric Background 3
Source GDJ
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin