There are many carbon patterns, but this one is tiny.
Source Designova
Actually remixed from a pattern on Pixabay. But then noticed a very similar one on Openclipart.org uploaded by btj51q2.
Source Firkin
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A seamless web texture with illustration of pale color stains on canvas.
Source V. Hartikainen
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Black brick wall pattern. Brick your site up!
Source Alex Parker
Prismatic Geometric Pattern Background 2
Source GDJ
Prismatic Polka Dots Mark II 2 No Background
Source GDJ
An alternative colour scheme to the original seamless pattern.
Source Firkin