Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A large pattern with funky shapes and form. An original. Sort of origami-ish.
Source Luuk van Baars
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
Prismatic Snowflakes Pattern No Background
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Prismatic Abstract Background Design
Source GDJ
A seamless texture of a rough concrete surface.
Source V. Hartikainen
Like the name suggests, this background image consists of a pattern of dark bricks. It may be an option for you, if you are looking for something that looks like a brick wall for use as a background on web pages. It's not a masterpiece, but looks pretty nice when is tiled.
Source V. Hartikainen
Here's a tile-able wood background image for use in web design.
Source V. Hartikainen
The image depicts a seamless pattern of a tortoise in tortoiseshell (hexagon).
Source Yamachem
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
ZeroCC tileable wood boards texture, photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'From Snowdon to the Sea. Striking stories of North and South Wales', Marie Trevelyan, 1895.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Derived from an image that was uploaded to Pixabay by darkmoon1968
Source Firkin