Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Have you wondered about how it feels to be buried alive? Here is the pattern for it.
Source Hendrik Lammers
A bit strange this one, but nice at the same time.
Source Diogo Silva
The image is a seamless pattern of a fishnet.
Source Yamachem
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Remixed from a drawing in 'An Index to Deering's Nottinghamia Vetus et Nova', Rupert Chicken, 1899. The unit tile can be had by selecting the rectangle in Inkscape and using shift-alt-i
Source Firkin
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
Same classic 45-degree pattern, dark version.
Source Luke McDonald
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
Prismatic Groovy Concentric Background 4
Source GDJ
Stefan is hard at work, this time with a funky pattern of squares.
Source Stefan Aleksić
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
A pale yellow background pattern with vertical stripes. The stripes are partially faded. I think this background image turned out pretty well, especially those faded stripes.
Source V. Hartikainen