Zero CC bark from fur tree tileable texture, photographed and made by me. CC0
Source Sojan Janso
A free seamless background image with abstract texture of green "curtain".
Source V. Hartikainen
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
A browner version of the original weathered fence texture.
Source Firkin
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
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
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Dark blue concrete wall with some small dust spots.
Source Atle Mo
Luxury pattern, looking like it came right out of Paris.
Source Daniel Beaton
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
A seamless green background texture. The image is distributed under a Creative Commons License (like all of the images here).
Source V. Hartikainen