Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
The image depicts a seamless pattern of a Japanese family crest called "chidori" in Japanese .A chidori in Japanese means a plover in English.
Source Yamachem
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
Same as Silver Scales, but in black. Turn your site into a dragon with this great scale pattern.
Source Alex Parker
Number five from the same submitter, makes my job easy.
Source Dima Shiper
This one has rusty dark brown texture.
Source V. Hartikainen
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
8 by 8 pixels, and just what the title says.
Source pixilated
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
A light brushed aluminum pattern for your pleasure.
Source Tim Ward
Nothing like a clean set of bed sheets, huh?
Source Badhon Ebrahim
A dark brown fabric-like background texture with seamless pattern of winding stripes.
Source V. Hartikainen
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers