From an image on opengameart.org shared by rubberduck.
Source Firkin
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Prismatic Snowflakes Pattern No Background
Source GDJ
A seamless design of flowers remixed from a jpg on Pixabay by Prawny.
Source Firkin
Based on an image that was uploaded to Pixabay by devanath
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
A seamless tessellation pattern. To get the tile this is formed from, select the pattern in Inkscape and use shift+alt+i.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Inspired by a JPG that was uploaded to Pixabay by kokon_art
Source Firkin
This background pattern has futuristic look. So, maybe it could be used on websites or blogs dedicated to video games?!
Source V. Hartikainen
A bit strange this one, but nice at the same time.
Source Diogo Silva
One can never have too few rice paper patterns, so here is one more.
Source Atle Mo
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Prismatic Groovy Concentric Background 5 No Black
Source GDJ
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
A comeback for you: the popular Escheresque, now in black.
Source Patten
Greyscale version of a pattern that came out of playing with the 'slinky' plug-in for Paint.net
Source Firkin
A free web background image with a seamless concrete-like texture and an Indian-red color.
Source V. Hartikainen