From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Remixed from a drawing in 'Prehistoric Man: researches into the origin of civilisation in the old and the new world', Daniel Wilson, 1876.
Source Firkin
Here's a brown background pattern with subtle stripes. I hope you'll like the color. If not, feel free to change it using an image editor, if you know how of course. Personally, I'm using GIMP to create these backgrounds.
Source V. Hartikainen
Oh yes, it happened! A pattern in full color.
Source Atle Mo
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
This was formed by distorting an image of a background on Pixabay.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
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
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
High detail stone wall with minor cracks and specks.
Source Projecteightyfive
A seamless marble-like texture colored in light blue.
Source V. Hartikainen
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett