Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
Not the Rebel alliance, but a dark textured pattern.
Source Hendrik Lammers
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
Derived from a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Prismatic Hypnotic Pattern No Background
Source GDJ
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
A free seamless background texture of "timber wall" (colored in dark brown).
Source V. Hartikainen
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The following orange background pattern resembles a honeycomb.
Source V. Hartikainen
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
More in the paper realm, this time with fibers.
Source Jorge Fuentes
Dark pattern with some nice diagonal stitched lines crossing over.
Source Ashton
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
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin