From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
A dark striped seamless pattern suitable for use as a background on websites.
Source V. Hartikainen
A nice and simple white rotated tile pattern.
Source Another One
A dark background pattern/texture of a dimpled metal plate.
Source V. Hartikainen
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
A re-make of the Gradient Squares pattern.
Source Dimitar Karaytchev
A free green background pattern with a pattern of rhombuses on a seamless texture. Feel free to use it as a tiled background image on your web site.
Source V. Hartikainen
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Wild Oliva or Oliva Wilde? Darker than the others, sort of a medium dark pattern.
Source Badhon Ebrahim
Continuing the geometric trend, here is one more.
Source Mike Warner
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
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton