A repeating background of thick textured paper. Actually, it turned out to look like something between a paper and fabric.
Source V. Hartikainen
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Scanned some rice paper and tiled it up for you. Enjoy.
Source Atle Mo
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
You know you can’t get enough of these linen-fabric-y patterns.
Source James Basoo
A seamless pattern formed from a tile made from ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Prismatic Rounded Squares Grid 3 No Background
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Dark, lines, noise, tactile. You get the drift.
Source Anatoli Nicolae
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
One more updated pattern. Not really carbon fiber, but it’s the most popular pattern, so I’ll give you an extra choice.
Source Atle Mo