Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Black brick wall pattern. Brick your site up!
Source Alex Parker
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
An abstract Background pattern of purple twisty patterns.
Source TikiGiki
Alternative colour scheme for the original floral pattern.
Source Firkin
A seamless pattern formed from miutopia's cakes on a tablecloth.
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Washi (和紙?) is a type of paper made in Japan. Here’s the pattern for you!
Source Carolynne
The image depicts the Japanese Edo pattern called "seigaiha" or "青海波" meaning "blue -sea- wave".I hope it's suitable for the summer season.
Source Yamachem
This background pattern has futuristic look. So, maybe it could be used on websites or blogs dedicated to video games?!
Source V. Hartikainen
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
From a drawing in 'Worsborough; its historical associations and rural attractions', Joseph Wilkinson, 1879.
Source Firkin
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A seamless pattern formed from background pattern 102
Source Firkin
Based on an image that was uploaded to Pixabay by devanath
Source Firkin
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein