A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
This tiled background comes in red and consists of tiles that look like gemstones. It is more for blogs or social profiles, I think.
Source V. Hartikainen
Sometimes you just need the simplest thing.
Source Fabricio
A seamlessly tile-able grunge background image.
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
Prismatic Polka Dots 3 No Background
Source GDJ
Plywood Web Background background image for use in web design.
Source V. Hartikainen
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
Element of beach pattern with background.
Source Rones
Based on an image that was uploaded to Pixabay by devanath
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
A seamless paper background colored in pale yellow.
Source V. Hartikainen
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
A version without colours blended together to give a different look.
Source Firkin
A repeating background with wood/straw like texture.
Source V. Hartikainen
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
From a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
A set of paper filters. The base texture is generated the same way, only the compositing mode is varied.
Source Lazur URH
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Zero CC tileable seed texture, edited by me to be seamless from a Pixabay image. CC0
Source Sojan Janso
I’m starting to think I have a concrete wall fetish.
Source Atle Mo
A green background pattern with warped vertical stripes and a grunge look.
Source V. Hartikainen