Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
CC0 remixed from a drawing. Walter Crane, 1914, Firkin.
Source SliverKnight
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
Spice up your next school project with this icon background.
Source Swetha
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
Derived from an image that was uploaded to Pixabay by pugmom40
Source Firkin
The classic notebook paper with horizontal stripes.
Source Are Sundnes
Prismatic Polka Dots Mark II 3 No Background
Source GDJ
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
Could be paper, could be a Polaroid frame – up to you!
Source Chaos
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo