I guess this is inspired by the city of Ravenna in Italy and its stone walls.
Source Sentel
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Prismatic Groovy Concentric Background 5
Source GDJ
Feel free to download and use it, or see the rest of the dark background patterns that I have made. Anyway, I hope you will find something that you like.
Source V. Hartikainen
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
This could be a hippy vintage wallpaper.
Source Tileable Patterns
Not so subtle. These tileable wood patterns are very useful.
Source Elemis
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
From a drawing in 'Kingsdene', Maria Fetherstonehaugh, 1878.
Source Firkin
Scanned some rice paper and tiled it up for you. Enjoy.
Source Atle Mo
Lovely pattern with some good-looking non-random noise lines.
Source Zucx
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
Seamless pattern formed from a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin