Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova
From a drawing in 'Danmarks Riges Historie af J. Steenstrup, Kr. Erslev, A. Heise, V. Mollerup, J. A. Fridericia, E. Holm, A. D. Jørgensen', 1897.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
Colourful background achieved with gradient fills.
Source Firkin
Has nothing to do with toast, but it’s nice and subtle.
Source Pippin Lee
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Derived from an image that was uploaded to Pixabay by starchim01
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
CC0 remixed from a drawing. Walter Crane, 1914, Firkin.
Source SliverKnight
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
Looks like an old rug or a computer chip.
Source Patutin Sergey
Seamless Dark Grunge Texture. Here's a new grunge texture for use as a background.
Source V. Hartikainen