A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
Might not be super subtle, but quite original in its form.
Source Alex Smith
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
This is a seamless pattern which is derived from a flower petal image.
Source Yamachem
The tile for this is based on a repeating unit close to a design on Pixabay. It can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
The following repeating website background is colored in a blue gray color and resembles a concrete wall or something similar to it.
Source V. Hartikainen
Background pattern originally a PNG drawn in Paint.net
Source Firkin
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
Zero CC bark from fur tree tileable texture, photographed and made by me. CC0
Source Sojan Janso
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
This light yellow background pattern consists of an irregular pattern of spots. Here's a light background pattern with yellowish tint.
Source V. Hartikainen
A hint of orange color, and some crossed and embossed lines.
Source Adam Anlauf
Zero CC tileable hard cover cells, skin like, book texture. 4K, Scanned and made by me CC0
Source Sojan Janso