Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A new take on the black linen pattern. Softer this time.
Source Atle Mo
This one resembles a black concrete wall when is tiled. It should look great, at least with dark website themes.
Source V. Hartikainen
Detailed but still subtle and quite original. Lovely gray shades.
Source Kim Ruddock
From a drawing in 'Less Black than we're painted', James Payn, 1884.
Source Firkin
Prismatic Rounded Squares Grid 3 No Background
Source GDJ
This background pattern contains a seamless texture of bark. It's not very realistic, but I think it looks quite nice.
Source V. Hartikainen
You may use it as is, or modify it as you like.
Source V. Hartikainen
New paper pattern with a slightly organic feel to it, using some thin threads.
Source Atle Mo
Inspired by a design found in 'Konstantinápolyi emlékeim', Miklos Chriszto, 1893.
Source Firkin
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Pattern produced in Paint.net using the Vibrato plug-in.
Source Firkin
By popular request, an outline version of the pentagon pattern.
Source Atle Mo
Prismatic Groovy Concentric Background
Source GDJ
From a drawing of the coat of arms of the Ottoman Empire on Wikimedia.
Source Firkin
This one looks like a cork panel. Feel free to use it as a tiled background on your blog or website.
Source V. Hartikainen
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
More carbon fiber for your collections. This time in white or semi-dark gray.
Source Badhon Ebrahim
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin
ZeroCC tileable mossy (lichen) stone texture, edited from pixabay. CC0
Source Sojan Janso
Prismatic Hexagonalist Pattern No Background
Source GDJ