A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Prismatic Hexagonalist Pattern No Background
Source GDJ
A mid-tone gray pattern with some cement looking texture.
Source Hendrik Lammers
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Prismatic Chevrons Pattern 5 With Background
Source GDJ
This one is amazing, truly original. Go use it!
Source Viahorizon
Tiny little flowers growing on your screen. Nice, huh?
Source Themes Tube
A free web background image with a seamless concrete-like texture and an Indian-red color.
Source V. Hartikainen
A free repetitive background with a dark concrete wall like texture. This one may be used in dark web site designs.
Source V. Hartikainen
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Prismatic Abstract Geometric Background derived from an image on Pixabay.
Source GDJ
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
All good things come in threes, so I give you the third in my little concrete wall series.
Source Atle Mo
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
The image depicts polka dot seamless pattern.
Source Yamachem
Colour version of the original pattern.
Source Firkin
A seamless background of warped stripes on paper.
Source V. Hartikainen
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
A fun-looking elastoplast/band-aid pattern. A hint of orange tone in this one.
Source Josh Green