People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Prismatic Groovy Concentric Background No Black
Source GDJ
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
Prismatic Snowflakes Pattern No Background
Source GDJ
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
It’s big, it’s gradient—and it’s square.
Source Brankic1979
A very dark asfalt pattern based off of a photo taken with my iPhone.
Source Atle Mo
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
A browner version of the original weathered fence texture.
Source Firkin
This one needs to be used in small areas; you can see it repeat.
Source Luca
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
Zero CC Mossy stone tileable texture, photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
One can never have too few rice paper patterns, so here is one more.
Source Atle Mo
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Seamless Green Tile Background
Source V. Hartikainen
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso