Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
Remixed from an image on Pixabay uploaded by Prawny
Source Firkin
A seamless pattern formed from miutopia mug remixes on a tablecloth.
Source Firkin
A seamless pattern the starting point for which was a 'light rays' rendering in Paint.net.
Source Firkin
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i
Source Firkin
Prismatic Basic Pattern 2 No Background
Source GDJ
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion