Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
The starting point for this was drawn on the web site steamcoded.org/PolyskelionMaker.svg
Source Firkin
Zero CC tileable hard cover red book, scanned and made by me. CC0
Source Sojan Janso
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Just like the black maze, only in light gray. Duh.
Source Peax
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857
Source Firkin
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo