Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Abstract Ellipses Background Grayscale
Source GDJ
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
From a drawing in 'Cassell's Library of English Literature', Henry Morley, 1883.
Source Firkin
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
Sort of reminds me of those old house wallpapers.
Source Tish
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Luxurious looking pattern (for a T-shirt maybe?) with a hint of green.
Source Simon Meek
Number five from the same submitter, makes my job easy.
Source Dima Shiper
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
Run a restaurant blog? Here you go. Done.
Source Andrijana Jarnjak
Prismatic Triangular Seamless Pattern III With Background
Source GDJ
You were craving more leather, so I whipped this up by scanning a leather jacket.
Source Atle Mo