Might not be super subtle, but quite original in its form.
Source Alex Smith
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Prismatic Hypnotic Pattern No Background
Source GDJ
Prismatic Chevrons Pattern 5 With Background
Source GDJ
Prismatic Curved Diamond Pattern 2 No Background
Source GDJ
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
Remixed from a drawing in 'Some account of the Worshipful Company of Ironmongers', John Nicholl, 1866.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Zero CC tileable hard cover cells book texture, 4k, scanned and made by me. CC0
Source Sojan Janso
Same as Silver Scales, but in black. Turn your site into a dragon with this great scale pattern.
Source Alex Parker
Same classic 45-degree pattern, dark version.
Source Luke McDonald
This is the remix of "Background pattern 115" uploaded by "Firkin".Thanks.
Source Yamachem
This is a grid, only it’s noisy. You know. Reminds you of those printed grids you draw on.
Source Vectorpile
The basic shapes never get old. Simple triangle pattern.
Source Atle Mo
Produced using the clouds, flames and glass blocks plug-ins in Paint.net and the resulting .PNG vectorised with Vector Magic.
Source Firkin
Inspired by a design found in 'Konstantinápolyi emlékeim', Miklos Chriszto, 1893.
Source Firkin
This makes me wanna shoot some pool! Sweet green pool table pattern.
Source Caveman