The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
Seamless Green Tile Background
Source V. Hartikainen
Prismatic Polka Dots Mark II 3 No Background
Source GDJ
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
A nice one indeed, but I have a feeling we have it already? If you spot a copy, let me know on Twitter.
Source Graphiste
Prismatic Polka Dots 3 No Background
Source GDJ
A seamless pattern based on a tile that can be achieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless pattern with wide vertical stripes colored in pale yellow.
Source V. Hartikainen
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i
Source Firkin
From a drawing in 'Hyde Park from Domesday-Book to date', John Ashton, 1896.
Source Firkin
A free repetitive background with a dark concrete wall like texture. This one may be used in dark web site designs.
Source V. Hartikainen
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Based on an image that was uploaded to Pixabay by devanath
Source Firkin
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
The original enhanced with some gradients.
Source Firkin
From an image on opengameart.org shared by rubberduck.
Source Firkin
Geometric triangles seem to be quite hot these days.
Source Pixeden
Super subtle indeed, a medium gray pattern with tiny dots in a grid.
Source Designova