Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
The image depicts a seamless pattern of a fishnet with a plenty of fish.It may be a lucky charm for fishermen.
Source Yamachem
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Abstract Tiled Background Extended 12
Source GDJ
Based on an image that was uploaded to Pixabay by devanath
Source Firkin
Black & white version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Pass parameters to the URL or edit the source code variables to configure the graph paper for the division desired.
Source JayNick
Not the Rebel alliance, but a dark textured pattern.
Source Hendrik Lammers
From a drawing in 'Kingsdene', Maria Fetherstonehaugh, 1878.
Source Firkin
The image depicts a shell seamless pattern.I used an OCAL clipart called "Shell" uploaded by "jgm104".Thanks.
Source Yamachem
Oh yes, it happened! A pattern in full color.
Source Atle Mo
A very slick dark rubber grip pattern, sort of like the grip on a camera.
Source Sinisha
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
This could be a hippy vintage wallpaper.
Source Tileable Patterns
Vertical lines with a bumpy, yet crisp, feel to it.
Source Raasa
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
Here's a tile-able wood background image for use in web design.
Source V. Hartikainen
Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio