Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Pattern Background, Texture, Photoshop Structure style CC0 texture.
Source Darkmoon1968
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Small dots with minor circles spread across to form a nice mosaic.
Source John Burks
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
As the original image 's page size is too large for its image size, I remixed it.
Source Yamachem
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
From a drawing in 'An Old Maid's Love. A Dutch tale told in English', Maarten Maartens, 1891.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
It’s a hole, in a pattern. On your website. Dig it!
Source Josh Green
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
Seamless tile drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
Background formed from the original with an emboss effect
Source GDJ
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
White circles connecting on a light gray background.
Source Mark Collins