Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Geometric lines are always hot, and this pattern is no exception.
Source Listvetra
From a drawing in 'Less Black than we're painted', James Payn, 1884.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
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 'A Life Interest', Mrs Alexander, 1888.
Source Firkin
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso
The name alone is awesome, but so is this sweet dark pattern.
Source Federica Pelzel
Hey, you never know when you’ll need a bird pattern, right?
Source Pete Fecteau
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
A new take on the black linen pattern. Softer this time.
Source Atle Mo
Colour version of the original seamless pattern.
Source Firkin
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin