Green Web Background, Seamless tile.
Source V. Hartikainen
To get the repeating unit, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
This metal background pattern resembles a metal plate with rivets. Solid rivets on a metal plate.
Source V. Hartikainen
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
A free seamless background with pink spots.
Source V. Hartikainen
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
Dark and hard, just the way we like it. Embossed triangles makes a nice pattern.
Source Ivan Ginev
Inspired by a 1930s wallpaper pattern I saw on TV.
Source Firkin
A seamless pattern formed from a square tile based on a jpg on Pixabay. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
A pattern derived from repeating unit cells each derived from part of a mosaic in paint.net. The starting point for the mosaic was a picture of some prawns!
Source Firkin
Small dots with minor circles spread across to form a nice mosaic.
Source John Burks
Vector version of a JPG that was uploaded to Pixabay by theasad121
Source Firkin