Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
A seamless pattern formed from a tile made from ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This could be a hippy vintage wallpaper.
Source Tileable Patterns
The image depicts a seamless pattern of pine tree leaves.
Source Yamachem
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
Prismatic Geometric Pattern Background 2 No Black
Source GDJ
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
A seamless pale yellow paper background with a pattern of animal tracks.
Source V. Hartikainen
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a design in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
Turn your site into a dragon with this great scale pattern.
Source Alex Parker
This is the remix of "polka dot seamless pattern".The image depicts polka dot seamless pattern.
Source Yamachem
Stefan is hard at work, this time with a funky pattern of squares.
Source Stefan Aleksić
Prismatic Polka Dots Mark II 3 No Background
Source GDJ
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin