There are many carbon patterns, but this one is tiny.
Source Designova
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
A dark metallic background with a pattern of stamped dots. Here's a dark "metallic" background pattern for you.
Source V. Hartikainen
A pattern formed from repeated instances of corner decoration 8. To get the basic tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
Adapted from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
A bit like some carbon, or knitted netting if you will.
Source Anna Litvinuk
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A black tile-able background with paper-like texture.
Source V. Hartikainen
Light and tiny, just the way you like it.
Source Rohit Arun Rao
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
A background pattern with a look of rough fabric.
Source V. Hartikainen
These dots are already worn for you, so you don’t have to.
Source Matt McDaniel
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Zero CC Mossy stone tileable texture, photographed and made by me. CC0
Source Sojan Janso
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Nicely executed tiling for an interesting pattern.
Source Ignasi Àvila Padró
Geometric triangles seem to be quite hot these days.
Source Pixeden