The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Prismatic Abstract Geometric Background 5
Source GDJ
One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
Zero CC tileable hard cover cells, skin like, book texture. 4K, Scanned and made by me CC0
Source Sojan Janso
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
This is indeed a bit strange, but here’s to the crazy ones!
Source Christopher Buecheler
The image depicts a seamless pattern of a tortoise in tortoiseshell (hexagon).
Source Yamachem
Used in small doses, this could be a nice subtle pattern. Used on a large surface, it’s dirty!
Source Paul Reulat
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Dark Tile-able Grunge Texture. I think this texture can be classified as grunge. It's free and seamless, as always.
Source V. Hartikainen
This background image has seamless texture that resembles a surface of gray stone.
Source V. Hartikainen
Colour version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
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
Prismatic Groovy Concentric Background 4 No Black
Source GDJ
Colour version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
Source Firkin
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin