A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
These dots are already worn for you, so you don’t have to.
Source Matt McDaniel
Feel free to download and use it, or see the rest of the dark background patterns that I have made. Anyway, I hope you will find something that you like.
Source V. Hartikainen
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A dark one with geometric shapes and dotted lines.
Source Mohawk Studios
Colorful Floral Background 3 No Black
Source GDJ
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
A very dark spotted twinkle pattern for your twinkle needs.
Source Badhon Ebrahim
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Zero CC tileable ground (#2) cracked, crackled texture, made by me. CC0
Source Sojan Janso
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
Wasn't satisfied with the original's colouring. Too much component transfer and colormatrixes yet the results are lacking a bit. So this time it is a simple black to transparent fade, making it possible remixing easily once there will be other blending modes supported as well. Probably in inkscape 0.92.
Source Lazur URH
A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
In the spirit of WWDC 2011, here is a dark iOS inspired linen pattern.
Source Atle Mo