The image depicts a seamless pattern of a Japanese family crest called "chidori" in Japanese .A chidori in Japanese means a plover in English.
Source Yamachem
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Prepared mostly as a raster in Paint.net and vectorised.
Source Firkin
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
So tiny, just 7 by 7 pixels – but still so sexy. Ah yes.
Source Dmitriy Prodchenko
A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
A seamless pattern based on a tile that can be achieved 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
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
Prismatic Groovy Concentric Background 2
Source GDJ
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios