Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
Formed from decorative divider 184 in paint.net. Vectorised with Vector Magic.
Source Firkin
ZeroCC tileable wood boards texture, photographed and made by me. CC0
Source Sojan Janso
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
Looks like an old rug or a computer chip.
Source Patutin Sergey
A seamless gray background texture suitable for use on websites. To me, it has the look of stone. Feel free to modify it to meet your needs (by making it a bit lighter or darker, for example).
Source V. Hartikainen
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
I’m guessing this is related to the Sony Vaio? It’s a nice pattern no matter where it’s from.
Source Zigzain
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
Background pattern made in "Grunge-Like" style. Available in both SVG and JPG formats. Edit to your needs then click the download button.
Source V. Hartikainen
Remixed from an image on Pixabay, the original having been uploaded by darkmoon1968.
Source Firkin
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
A free tileable background colored in off-white (antique white) color.
Source V. Hartikainen
Zero CC tileable Laminate wood texture, photographed and made by me. CC0
Source Sojan Janso
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
From a drawing in 'Az Osztrák-Magyar Monarchia irásban és képben', 1885.
Source Firkin
From a drawing in 'La Principauté de Liège et les Pays-Bas au XVIe siècle', Société des Bibliophiles Liégeois ,1887.
Source Firkin
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
You know I love paper patterns. Here is one from Stephen. Say thank you!
Source Stephen Gilbert
I’m starting to think I have a concrete wall fetish.
Source Atle Mo
Remixed from a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo