The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Colour version of the original pattern.
Source Firkin
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
Beautiful dark noise pattern with some dust and grunge.
Source Vincent Klaiber
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless pattern formed from a rectangular tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!
Source Dertig Media
Prismatic Curved Diamond Pattern 4 No Background
Source GDJ
Zero CC tileable grass texture, photographed and made by me. CC0
Source Sojan Janso
A textured orange background pattern with vertical stripes.
Source V. Hartikainen
Remixed from a JPG that was uploaded to Pixabay by Osckar
Source Firkin
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Prismatic Groovy Concentric Background 5
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Can’t believe we don’t have this in the collection already! Slick woven pattern with crisp details.
Source Max Rudberg
Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
A seamless texture of an abstract wall colored in shades of light orange brown.
Source V. Hartikainen
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
Black And White Floral Pattern Background Inverse
Source GDJ
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