CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
Heavily remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Original seamless pattern with an Inkscape filter.
Source Firkin
This background pattern contains worn out colorful stripes as a texture.
Source V. Hartikainen
The image depicts a seamless pattern of the design which includes a stylized lotus and a stylized crane.I referred to the original image in a book which is into public domain.
Source Yamachem
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Prismatic Geometric Pattern Background 2 No Black
Source GDJ
That’s what it is, a dark dot. Or sort of carbon looking.
Source Tsvetelin Nikolov
The base gradient edited so now more details are rendered.
Source Lazur URH
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
From a design in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin