From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Stefan is hard at work, this time with a funky pattern of squares.
Source Stefan Aleksić
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
From a drawing in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
This background has abstract texture with some similarities to wood.
Source V. Hartikainen
Tile available in Inkscape using shift-alt-i on the selected rectangle
Source Firkin
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
An abstract texture of black metal pipes (seamless).
Source V. Hartikainen
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
Vertical lines with a bumpy, yet crisp, feel to it.
Source Raasa
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin