In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Prismatic Curved Diamond Pattern No Background
Source GDJ
ZeroCC tileable mossy (lichen) stone texture, edited from pixabay. CC0
Source Sojan Janso
Pattern produced in Paint.net using the Vibrato plug-in.
Source Firkin
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett