The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Not a flat you live inside, like in the UK – but a flat piece of cardboard.
Source Appleshadow
A light gray background pattern with seamless fabric-like texture and almost unnoticeable stripes.
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by starchim01
Source Firkin
A fun-looking elastoplast/band-aid pattern. A hint of orange tone in this one.
Source Josh Green
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Not so subtle. These tileable wood patterns are very useful.
Source Elemis
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ
8 by 8 pixels, and just what the title says.
Source pixilated
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Subtle scratches on a light gray background.
Source Andrey Ovcharov
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
Prismatic Floral Background No Black
Source GDJ
You know you can’t get enough of these linen-fabric-y patterns.
Source James Basoo
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Retro Circles Background 4 No Black
Source GDJ
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
A pattern derived from repeating unit cells each derived from part of a mosaic in paint.net. The starting point for the mosaic was a picture of some prawns!
Source Firkin