Might not be super subtle, but quite original in its form.
Source Alex Smith
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS
Non-seamless pattern drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
Submitted in a cream color, but you know how I like it.
Source Devin Holmes
Subtle scratches on a light gray background.
Source Andrey Ovcharov
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
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
Vector version of a JPG that was uploaded to Pixabay by theasad121
Source Firkin
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
Zero CC tileable Laminate wood texture, photographed and made by me. CC0
Source Sojan Janso
An alternative colour scheme to the original seamless pattern.
Source Firkin
A pale olive green background with a seamless texture.
Source V. Hartikainen
I skipped number 3, because it wasn’t all that great. Sorry.
Source Dima Shiper
Remixed from a drawing in 'Analecta Eboracensia', Thomas Widdrington, 1897.
Source Firkin
Redrawn based on a drawing in 'По Сѣверо-Западу Россіи' Konstantin Sluchevsky, 1897.
Source Firkin
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Imagine you zoomed in 1000X on some fabric. But then it turned out to be a skeleton!
Source Angelica
An alternative colour scheme to the original seamless pattern.
Source Firkin
Prepared mostly as a raster in Paint.net and vectorised.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin