There are many carbon patterns, but this one is tiny.
Source Designova
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Prismatic Geometric Pattern Background No Black
Source GDJ
Retro Circles Background 7 No Black
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Black brick wall pattern. Brick your site up!
Source Alex Parker
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
Remixed from a JPG that was uploaded to Pixabay by susanlu4esm
Source Firkin
Light gray paper pattern with small traces of fiber and some dust.
Source Atle Mo
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
Sharp but soft triangles in light shades of gray.
Source Pixeden
A heavy hitter at 400x400px, but lovely still.
Source Breezi
Remixed from a JPG that was uploaded to Pixabay by theasad121
Source Firkin
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges