People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Vector version of a JPG that was uploaded to Pixabay by theasad121
Source Firkin
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
Prismatic Groovy Concentric Background 4
Source GDJ
Abstract Tiled Background Extended 10
Source GDJ
Remixed from a drawing in 'Prehistoric Man: researches into the origin of civilisation in the old and the new world', Daniel Wilson, 1876.
Source Firkin
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
A repeating background with wood/straw like texture.
Source V. Hartikainen
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Seamless Prismatic Geometric Pattern With Background
Source GDJ
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
A background pattern with a look of rough fabric.
Source V. Hartikainen
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
The original has been presented as black on transparent and stored in the pattern definitions. To retrieve the unit tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Paper model of a tetrahedron. Modelo de papel de um tetraedro.
Source laobc
Utilising a bird from s-light and some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A seamlessly tileable pink background texture.
Source V. Hartikainen
All good things come in threes, so I give you the third in my little concrete wall series.
Source Atle Mo
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin