The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.
Source Firkin
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Gold Triangular Seamless Pattern No Background
Source GDJ
ZeroCC tileable wood boards texture, photographed and made by me. CC0
Source Sojan Janso
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Same as the black version, but now in shades of gray. Very subtle and fine grained.
Source Atle Mo
From a drawing in 'Friend or Fortune? The story of a strange year', Robert Overton, 1897.
Source Firkin
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
Super detailed 16×16 tile that forms a beautiful pattern of straws.
Source Pavel
There are many carbon patterns, but this one is tiny.
Source Designova
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
This was formed by distorting an image of a background on Pixabay.
Source Firkin
That’s what it is, a dark dot. Or sort of carbon looking.
Source Tsvetelin Nikolov
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A seamless pattern drawn originally in Paint.net by distorting a slice of background pattern 116 and copying the resulting triangle numerous times.
Source Firkin
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
A seamless background of warped stripes on paper.
Source V. Hartikainen
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.