Could be paper, could be a Polaroid frame – up to you!
Source Chaos
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Black brick wall pattern. Brick your site up!
Source Alex Parker
Prismatic Groovy Concentric Background
Source GDJ
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
A very slick dark rubber grip pattern, sort of like the grip on a camera.
Source Sinisha
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Snowflakes Pattern 2 No Background
Source GDJ
A light gray wall or floor (you decide) of concrete.
Source Atle Mo
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
Prismatic Abstract Geometric Background 3
Source GDJ
Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
A repeating background with wood/straw like texture.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
No, not the band but the pattern. Simple squares in gray tones, of course.
Source Atle Mo
There are quite a few grid patterns, but this one is a super tiny grid with some dust for good measure.
Source Dominik Kiss
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