Might not be super subtle, but quite original in its form.
Source Alex Smith
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Prismatic Snowflakes Pattern 3 No Background
Source GDJ
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ
Remixed from a drawing that was uploaded to Pixabay by DavidZydd
Source Firkin
Farmer could be some sort of fabric pattern, with a hint of green.
Source Fabian Schultz
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Use shift+alt+i on the selected rectangle in Inkscape to get the tile this is based on
Source Firkin
Prismatic Abstract Geometric Background derived from an image on Pixabay.
Source GDJ
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Derived from a drawing in 'Elfrica. An historical romance of the twelfth century', Charlotte Boger, 1885
Source Firkin
This one looks like a cork panel. Feel free to use it as a tiled background on your blog or website.
Source V. Hartikainen
Psychedelic Geometric Background No Black
Source GDJ
This ladies and gentlemen, is texturetastic! Love it.
Source Adam Pickering
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Zero CC tileable moss or lichen covered stone texture, edited from pixabay. CC0
Source Sojan Janso
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo