The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Number five from the same submitter, makes my job easy.
Source Dima Shiper
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
I’m not going to lie – if you submit something with the words Norwegian and Rose in it, it’s likely I’ll publish it.
Source Fredrik Scheide
A seamless pattern made from the gold Penrose triangle by GDJ and the two remixes
Source Firkin
Zero CC Mossy stone tileable texture, photographed and made by me. CC0
Source Sojan Janso
A comeback for you: the popular Escheresque, now in black.
Source Patten
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
Farmer could be some sort of fabric pattern, with a hint of green.
Source Fabian Schultz
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber