A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
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
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Submitted as a black pattern, I made it light and a few steps more subtle.
Source Andy
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
Free tiled background with colorful stripes and white splatter.
Source V. Hartikainen
More in the paper realm, this time with fibers.
Source Jorge Fuentes
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Adapted heavily from a JPG that was uploaded to Pixabay by Viscious-Speed.
Source Firkin
With a name like this, it has to be hot. Diagonal lines in light shades.
Source Isaac
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin