Here's a seamless brown cork board background texture. Feel free to download or reshare if you like.
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
This is a seamless pattern of a woody texture.The original image is here:https://pixabay.com/ja/users/ClassicallyPrinted-1302233/
Source Yamachem
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Seamless Green Tile Background
Source V. Hartikainen
A seamless texture of worn out "cardboard".
Source V. Hartikainen
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
Seamless pattern inspired by a drawing on Pixabay. To get the tile this is formed from, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Prismatic Abstract Background Design
Source GDJ
A slightly more textured pattern, medium gray. A bit like a potato sack?
Source Bilal Ketab
An abstract web texture of a polished blue stone (or does it look more like ice).
Source V. Hartikainen
From a drawing in 'Jardyne's Wife', Charles Wills, 1891.
Source Firkin
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
A comeback for you: the popular Escheresque, now in black.
Source Patten
f you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal