People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
Tiny circle waves, almost like the ocean.
Source Sagive
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Continuing the geometric trend, here is one more.
Source Mike Warner
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
Uses spirals from Pixabay. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Seamless Prismatic Geometric Pattern With Background
Source GDJ
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
From a drawing in 'La Principauté de Liège et les Pays-Bas au XVIe siècle', Société des Bibliophiles Liégeois ,1887.
Source Firkin
I’m not going to lie – if you submit something with the words Norwegian and Rose in it, it’s likely I’ll publish it.
Source Fredrik Scheide