This is lovely, just the right amount of subtle noise, lines and textures.
Source Richard Tabor
Seamless pattern made from a tile that can be obtained in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
A black tile-able background with paper-like texture.
Source V. Hartikainen
From a drawing in 'Hundert Jahre in Wort und Bild', S. Stefan, 1899.
Source Firkin
This background pattern contains a texture of yellow wood planks. I think it looks quite original.
Source V. Hartikainen
A heavy hitter at 400x400px, but lovely still.
Source Breezi
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
Zero CC tileable moss or lichen covered stone texture, edited from pixabay. CC0
Source Sojan Janso