As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Turn your site into a dragon with this great scale pattern.
Source Alex Parker
A pale olive green background with a seamless texture.
Source V. Hartikainen
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
This metal background pattern resembles a metal plate with rivets. Solid rivets on a metal plate.
Source V. Hartikainen
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin
Thin lines, noise and texture creates this crisp dark denim pattern.
Source Marco Slooten
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
Thin lines, noise and texture creates this crisp dark denim pattern.
Source Marco Slooten
An attempt for cleaning up the original image in a few steps.
Source Lazur URH
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso