Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
One more sharp little tile for you. Subtle circles this time.
Source Blunia
A free background image with a seamless texture of cardboard. This texture of cardboard looks quite realistic, especially when is actually tiled.
Source V. Hartikainen
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
Prismatic Polka Dots Mark II No Background
Source GDJ
Sometimes you just need the simplest thing.
Source Fabricio
Drawn in Paint.net and vectorised in Vector Magic
Source Firkin
A bit strange this one, but nice at the same time.
Source Diogo Silva
Seamless Prismatic Geometric Pattern With Background
Source GDJ
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Derived from a drawing in 'The Murmur of the Shells', Samuel Cowen, 1879.
Source Firkin
ZeroCC tileable mossy (lichen) stone texture, edited from pixabay. CC0
Source Sojan Janso
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
As simple and subtle as it gets. But sometimes that’s just what you want.
Source Designova
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
This background pattern looks like bamboo to me. Feel free to download it for your website (for your blog perhaps?).
Source V. Hartikainen
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic 3D Isometric Tessellation Pattern 6
Source GDJ
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A repeating background of beige (or is it more vanilla yellow) textured stripes. One more background with stripes.
Source V. Hartikainen
The image is a remix of "edo pattern-samekomon".I changed the color of dots from black to white and added BG in light-yellow.
Source Yamachem
From a drawing in 'Handbook of the excursions proposed to be made by the Lincoln Diocesan Architectural Society, on the 27th and 28th of May, 1857', Edward Trollope, 1857.
Source Firkin