Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom
Greyscale version of a pattern that came out of playing with the 'slinky' plug-in for Paint.net
Source Firkin
A seamless background pattern with a texture of wood planks. This wood background pattern has vertically arranged planks. You may try to rotate it 90°, to see how it will look like when the wood planks are arranged horizontally.
Source V. Hartikainen
Retro Circles Background 5 No Black
Source GDJ
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
With a name like this, it has to be hot. Diagonal lines in light shades.
Source Isaac
Prismatic Polka Dots Mark II 3 No Background
Source GDJ
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
I’m starting to think I have a concrete wall fetish.
Source Atle Mo
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
A bit of scratched up grayness. Always good.
Source Dmitry
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
A seamless striped fabric-like texture colored in a dark reddish brown color.
Source V. Hartikainen
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
Feel free to download this "Dark Wood" background texture for your web site. The background tiles seamlessly!
Source V. Hartikainen
Prismatic Geometric Tessellation Pattern 4 No Background
Source GDJ