This metal background pattern resembles a metal plate with rivets. Solid rivets on a metal plate.
Source V. Hartikainen
Inspired by this, I came up with this pattern. Madness!
Source Atle Mo
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A light background pattern with diagonal stripes. Here's a simple light striped background for you.
Source V. Hartikainen
Retro Circles Background 5 No Black
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
ZeroCC tileabel stone granite texture, edited from pixabay. CC0
Source Sojan Janso
Seamless Light Background Texture.
Source V. Hartikainen
Here's a seamless brown cork board background texture. Feel free to download or reshare if you like.
Source V. Hartikainen
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
One more sharp little tile for you. Subtle circles this time.
Source Blunia
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
A free background pattern with abstract green tiles.
Source V. Hartikainen
Could be paper, could be a Polaroid frame – up to you!
Source Chaos
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
He influenced us all. “Don’t be sad because it’s over. Smile because it happened.”
Source Atle Mo
Colourful background achieved with gradient fills.
Source Firkin
This texture looks like old leather. It should look great as a background on web pages.
Source V. Hartikainen
Seamless tile drawn in Paint.net and vectorised in Vector Magic.
Source Firkin