A free seamless background with pink spots.
Source V. Hartikainen
Fix and cc0 to get the tile this is based on.
Source SliverKnight
This background pattern contains worn out colorful stripes as a texture.
Source V. Hartikainen
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
This background pattern has futuristic look. So, maybe it could be used on websites or blogs dedicated to video games?!
Source V. Hartikainen
Prismatic Hexagonalist Pattern No Background
Source GDJ
This was submitted in a beige color, hence the name. Now it’s a gray paper pattern.
Source Konstantin Ivanov
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
A seamless pattern formed from a tile made from page ornament 22. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This is so subtle: We’re talking 1% opacity. Get your squint on!
Source Atle Mo
Tiny little fibers making a soft and sweet look.
Source Badhon Ebrahim
Dark Tile-able Grunge Texture. I think this texture can be classified as grunge. It's free and seamless, as always.
Source V. Hartikainen
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
The image depicts a seamless pattern of Japanese Edo pattern called "kikkou-matsu" or "亀甲松" meaning " tortoiseshell-pinetree".The real pinetree is like this: https://jp.pinterest.com/pin/500744052301065077/
Source Yamachem
Light gray grunge wall with a nice texture overlay.
Source Adam Anlauf
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
A repeating gloomy background image. This one consists of a pattern of black chains layered on top of a dark textured background.
Source V. Hartikainen
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen