Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
This one needs to be used in small areas; you can see it repeat.
Source Luca
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
White circles connecting on a light gray background.
Source Mark Collins
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
Heavily remixed from a drawing that was uploaded to Pixabay by ractapopulous
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
An abstract pale yellow paper-like background with stains colored in yellow and green.
Source V. Hartikainen
Floral patterns will never go out of style, so enjoy this one.
Source Lasma
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
The tile this is based on can be had by selecting the rectangle in Inkscape and using 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
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper