Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
Honestly, who does not like a little pipe and mustache?
Source Luca Errico
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
Remixed from a raster on Pixabay that was uploaded by ArtsyBee.
Source Firkin
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
Geometric triangles seem to be quite hot these days.
Source Pixeden
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868.
Source Firkin
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
This background pattern looks like bamboo to me. Feel free to download it for your website (for your blog perhaps?).
Source V. Hartikainen
The basic shapes never get old. Simple triangle pattern.
Source Atle Mo
This background pattern contains a seamless texture of bark. It's not very realistic, but I think it looks quite nice.
Source V. Hartikainen
Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin