Lovely pattern with some good-looking non-random noise lines.
Source Zucx
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
Derived from an image that was uploaded to Pixabay by starchim01
Source Firkin
Medium gray fabric pattern with 45-degree lines going across.
Source Atle Mo
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
Luxurious looking pattern (for a T-shirt maybe?) with a hint of green.
Source Simon Meek
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A seamless stone-like background for blogs or any other type of websites.
Source V. Hartikainen
This one needs to be used in small areas; you can see it repeat.
Source Luca
A free black metallic background pattern. Here's a new pattern I made that looks metallic.
Source V. Hartikainen
Bumps, highlight and shadows – all good things.
Source Badhon Ebrahim
Prismatic Groovy Concentric Background 4 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
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i
Source Firkin
Kaleidoscope Prismatic Abstract No Background
Source GDJ
This one has rusty dark brown texture.
Source V. Hartikainen
Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
White circles connecting on a light gray background.
Source Mark Collins
Prismatic Polka Dots Mark II 3 No Background
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus