Not so subtle. These tileable wood patterns are very useful.
Source Elemis
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
The image depicts a shell seamless pattern.I used an OCAL clipart called "Shell" uploaded by "jgm104".Thanks.
Source Yamachem
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
An abstract Background pattern of purple twisty patterns.
Source TikiGiki
Prismatic Geometric Pattern Background No Black
Source GDJ
Pattern formed from simple shapes. Black version.
Source Firkin
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
Remixed from a drawing in 'Some account of the Worshipful Company of Ironmongers', John Nicholl, 1866.
Source Firkin
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
It’s big, it’s gradient—and it’s square.
Source Brankic1979
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
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
There are many carbon patterns, but this one is tiny.
Source Designova
Prismatic Abstract Background Design
Source GDJ
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
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
Sounds French. Some 3D square diagonals, that’s all you need to know.
Source Graphiste
Remixed from a drawing in 'Line and form", Walter Crane, 1914.
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
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin