A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Classic 45-degree pattern, light version.
Source Luke McDonald
The tile this is based on was adapted from an image that was uploaded to Pixabay by frolicsomepl. It can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Luxury pattern, looking like it came right out of Paris.
Source Daniel Beaton
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Fix side and a seamless pattern formed from circles.
Source SliverKnight
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
A tile-able background for websites with paper-like texture and a grid pattern layered on top of it.
Source V. Hartikainen
Abstract Tiled Background Extended 10
Source GDJ
A free black metallic background pattern. Here's a new pattern I made that looks metallic.
Source V. Hartikainen
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
Derived from a drawing in 'Historiske Afhandlinger', Adolf Jorgensen, 1898.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Prismatic Polyskelion Pattern No Background
Source GDJ
A seamless pattern formed from miutopia's cakes on a tablecloth.
Source Firkin
Farmer could be some sort of fabric pattern, with a hint of green.
Source Fabian Schultz
A floral background formed from numerous clones of flower 117.
Source Firkin
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
It’s an egg, in the form of a pattern. This really is 2012.
Source Paul Phönixweiß
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen