A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
A heavy hitter at 400x400px, but lovely still.
Source Breezi
A free pink background pattern.
Source V. Hartikainen
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Someone was asking about how to achieve a fur pattern at #inkscape irc so tried to make a filter on it. Flood filled fractal noises rigged together. May someone find a good use for these.
Source Lazur URH
Classy golf-pants pattern, or crossed stripes if you will.
Source Will Monson
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
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
This background pattern contains a texture of yellow wood planks. I think it looks quite original.
Source V. Hartikainen
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
A seamless pattern formed from a square tile based on a jpg on Pixabay. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Number 5 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
f you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Prismatic Abstract Geometric Background 5
Source GDJ
This ladies and gentlemen, is texturetastic! Love it.
Source Adam Pickering