A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A comeback for you: the popular Escheresque, now in black.
Source Patten
Inspired by a pattern found in 'A General History of Hampshire, or the County of Southampton, including the Isle of Wight', Bernard Woodwood, 1861
Source Firkin
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
You know you love wood patterns, so here’s one more.
Source Richard Tabor
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
The file was named striped lens, but hey – Translucent Fibres works too.
Source Angelica
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
This is a hot one. Small, sharp and unique.
Source GraphicsWall
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
This one is amazing, truly original. Go use it!
Source Viahorizon
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
Zero CC tillable hard cover red book with X shape marks. Scanned and made by me.
Source Sojan Janso
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
Looks as if it's spray painted on the wall. You can be sure that this pattern will seamlessly fill your backgrounds on web pages.
Source V. Hartikainen