A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Lovely pattern with splattered vintage speckles.
Source David Pomfret
Inspired by a drawing in 'Poems', James Smith, 1881.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Classy golf-pants pattern, or crossed stripes if you will.
Source Will Monson
This background pattern contains a seamless texture of bark. It's not very realistic, but I think it looks quite nice.
Source V. Hartikainen
Just like your old suit, all striped and smooth.
Source Alex Berkowitz
Awesome name, great pattern. Who does not love space?
Source Nick Batchelor
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
We have some linen patterns here, but none that are stressed. Until now.
Source Jordan Pittman
The file was named striped lens, but hey – Translucent Fibres works too.
Source Angelica
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
Basket Fibers, Basket Texture, Braid Background style CC0 texture.
Source 1A-Photoshop
Derived from an image that was uploaded to Pixabay by starchim01
Source Firkin
Seamless Olive Green Web Background Image
Source V. Hartikainen