A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Colorful Floral Background 3 No Black
Source GDJ
A seamless green background texture. The image is distributed under a Creative Commons License (like all of the images here).
Source V. Hartikainen
This was formed by distorting an image of a background on Pixabay.
Source Firkin
8 by 8 pixels, and just what the title says.
Source pixilated
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
The base gradient edited so now more details are rendered.
Source Lazur URH
You can never get enough of these tiny pixel patterns with sharp lines.
Source Designova
A nice and simple white rotated tile pattern.
Source Another One
Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A yellow tiled background... Blurriness, bokeh effect and rectangles pattern in one mix.
Source V. Hartikainen
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
A bit of scratched up grayness. Always good.
Source Dmitry
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
I love the movie Pineapple Express, and I’m also liking this Pineapple right here.
Source Audee Mirza
Prismatic Polyskelion Pattern No Background
Source GDJ
Actually remixed from a pattern on Pixabay. But then noticed a very similar one on Openclipart.org uploaded by btj51q2.
Source Firkin