A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
This one needs to be used in small areas; you can see it repeat.
Source Luca
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
A nice and simple white rotated tile pattern.
Source Another One
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
These dots are already worn for you, so you don’t have to.
Source Matt McDaniel
From a drawing in 'A Life Interest', Mrs Alexander, 1888.
Source Firkin
The image depicts a seamless pattern made using a bird's face.
Source Yamachem
Prismatic Abstract Geometric Background 4
Source GDJ
The image depicts a seamless pattern of a tortoise in tortoiseshell (hexagon).
Source Yamachem
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'Uit de geschiedenis der Heilige Stede te Amsterdam', Yohannes Sterck, 1898.
Source Firkin
Here's a repeatable texture that resembles a light green concrete wall or something similar.
Source V. Hartikainen
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki