As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
This is the remix of "Strawberry Pattern Background" uploaded by "GDJ". Thanks. I realigned strawberries so as to get seamless and changed the BG color.
Source Yamachem
A dark pattern made out of 3×3 circles and a 1px shadow. This works well as a carbon texture or background.
Source Atle Mo
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
I guess this is inspired by the city of Ravenna in Italy and its stone walls.
Source Sentel
This beige background pattern resembles a concrete wall with engravings or something similar to it.
Source V. Hartikainen
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 free web background image with a seamless concrete-like texture and an Indian-red color.
Source V. Hartikainen
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
It was called Navy Blue, but I made it dark. You know, the way I like it.
Source Ethan Hamilton
Inspired by a JPG that was uploaded to Pixabay by kokon_art
Source Firkin
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo