That’s what it is, a dark dot. Or sort of carbon looking.
Source Tsvetelin Nikolov
Inspired by a 1930s wallpaper pattern I saw on TV.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
Semi-light fabric pattern made out of random pixels in shades of gray.
Source Atle Mo
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Background Wall, Art Abstract, white Well & CC0 texture.
Source Ractapopulous
A repeating background of thick textured paper. Actually, it turned out to look like something between a paper and fabric.
Source V. Hartikainen
Seamless pattern formed from a tile that can be extracted by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio