CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Hey, you never know when you’ll need a bird pattern, right?
Source Pete Fecteau
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
Could be paper, could be a Polaroid frame – up to you!
Source Chaos
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Background Wall, Art Abstract, Star Well & CC0 texture.
Source Ractapopulous
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
A dark brown fabric-like background texture with seamless pattern of winding stripes.
Source V. Hartikainen
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A background tile of dark textile. Made this a long time ago and just now decided to publish it.
Source V. Hartikainen