Sort of reminds me of those old house wallpapers.
Source Tish
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
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
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
I love these crisp, tiny, super subtle patterns.
Source Badhon Ebrahim
Spice up your next school project with this icon background.
Source Swetha
Remixed from a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
Retro Circles Background 7 No Black
Source GDJ
This was formed by distorting an image of a background on Pixabay.
Source Firkin
The image a seamless pattern derived from a weed which I can't identify.The original weed image is from here:https://jp.pinterest.com/pin/500744052301423641/
Source Yamachem
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki